Yes, I agree this is the 'killer app' for bitcoin.  In fact I emailed Kachingle about it weeks ago and received no response.

Kachingle, Flattr, Rewrd, all of them are doing the same thing (dividing up a predetermined monthly donation).  None of them offer the flexibility of bitcoin.

A html widget that can be pasted anywhere, and modules for Wordpress, Joomla, Drupal, and bitcoin modules that work like points/thank you modules for vBulleting, SMF and other forum systems are products that leverage bitcoins micropayment advantage over all other popular accepted methods.

I feel bitcoins big advantage in the marketplace isn't the anonymity as much as its miniscule transaction costs.  Building on that is the possible path to widespread, mainstream use.

Unfortunately I don't have the skills to build any of this stuff. 

It is trivial to make this button using mtgox checkout:

<form action="https://mtgox.com/merch/checkout" method="post" >
   <input type="hidden" name="business"      value="Your MtGox Username">
   <input type="hidden" name="currency_code"   value="BTC">
   <input type="hidden" name="item_name"      value="Donation to Blah">      
   <input type="hidden" name="amount"      value="5">
   <input type="hidden" name="return"      value="http://yourdomain.com/thanks">
   
   <input type="submit" value="Donate BTC" >
</form>


This will donate 5 BTC.

I think what's needed is MORE than just a widget.

A big part of the winning idea.... of Flattr.... is the idea of ONE FLAT BUDGETED AMOUNT per month... no matter how many items you "like" (click on) that month.

What's needed is a WEB SITE...   where users can create an account, and give it a monthly budget.    By design, Bitcoin does NOT have a monthly recurring payment system...   So, I guess the site would have to allow me to load it up with funds, and then specify my monthly budget.   Then, as I click on many different blogs/videos/etc that I like...  It would tally up how many I've clicked on that month, and divide the budget amongst all those content creators.

In other words.   I go to BitTip.com (or some such name).    I create an account.   I specify that I want to tip $10 (in Bitcoin) per month.    I then send $50 (in Bitcoin) to the special Bitcoin address to "top up" my account.    But, the site would only distribute $10 per month....leaving the remaining $40 for subsequent months.   If I click on 10 widgets from 10 different videos, blog items, and other content on the web, that month...  then each one will automatically receive $1 (in Bitcoin).   On the otherhand, if I click on 20 sites that month, then each one will receive $0.50 in Bitcoin.   In other words, my $10 is evenly distributed among ALL the sites I click on that month.    As soon as my remaining funds fall below my monthly budget (I had established) for the following month, I am sent an email...  reminding me to deposit more. 

This same system could be used for DONATIONS as well as "Tips".    For example, I might want to click the widget on Charities or Causes.... like Kiva.org or EFF.org    Or on actual content, like a great new artist on YouTube or a podcast or a blogger...   It works for anything that you want to GIVE to.   Even churches or political causes!

Besides the insanely affordable transaction fees that Bitcoin offers (free).... 

Here's the Kicker:     FLATTR TAKES A 10% CUT FROM EVERY SINGLE TRANSACTION IT PROCESSES

Is it just me, or is that highway robbery?   

That just leaves a VERY BAD taste in my mouth.....    That this operation takes 10% of the LOVE that the cumulative collective consciousness of humanity want to GIVE....

What gives them the right to take a full 10% !?!?!?

So, I think that an actual site system needs to be developed....   where one can create an account....   deposit funds....  set a monthly budget....   have an automated low-balance reminder by email notification system...    connected widgets for all types of sites (Think: Digg-style widgets for every blog item footer and sidebar)...  and an automated method of dividing the budgeted donations among all clicked sites for that month.

I know it's alot of work.   But Mt Gox has about 80% of this in place already.

It would have to be a separate name, with a very slick clean modern web 2.5 interface.    Easy enough for grandma to use.

Also....  It should accept normal credit cards to fund the payments.    Then, all donations that are allocated within the first 90 days from that credit card payment, would automatically be HELD back (delayed) for 90 days....  then, after 90 days, sent automatically.  (to prevent any possibility of chargebacks)

Because it's a donation, who can complain about the delay?   Really...?

I truly believe that:     THIS is THE KILLER APP for bitcoin's mainstream acceptance.

If executed properly, and marketed well...    including prominently advertising, "Why give Flattr 10% of all of your donations. We charge 0%  transaction fees."

Of course, the bank will charge some transaction fee on the initial deposit if it's made by credit card.  But that's not our fee.  That's the bank's fee.  No fees are charged on the actual donations.   And THAT could be enough of a competitive advantage.... to make people chose this method.   

"100% of your donation goes to who you specify.  (Not just 90% of it.)"

If the entire thing is automated...  what's the ongoing cost of running it?   Could the site be advertising supported?    If not, I suppose something like 0.1% would be ok.   

Just think:   If this were to really TAKE OFF...  0.1% of EVERY DONATION ON THE INTERNET....  could amount to a LOT of money.

You might want to record the idea in:

http://bt.irlbtc.com/view/1268.0

Actually I thought that was the big DISadvantage of Flattr/Kachingle et. al.

Let's say I'm at a blogger site and happen to really like his most recent blog entry.  I might want to tip him 0.05 BTC.  That doesn't mean I want to tip him 0.05 every month.  Maybe I'll never come back to that website again.  I don't want to make a lifetime commitment, just say 'thanks' once.

A bitcoin-based system could also be used to unlock content.  Maybe I'm trying to find a solution to a problem I'm having with my car.  The answer is in some automotive forum where general discussion is free, but specific solutions are in a locked topic that can only be opened by a one-time 'donation' of 0.10 BTC.

The big advantage of a bitcoin-based system would be the ability to do ad hoc donations with minimal transaction cost.  That is a significant competitve advantage for bitcoin.  As far as I can tell, nobody is doing that currently.

Fortunately, Flattr (and kachingle) don't work that way. At the end of each month, they look at the pages you "thanked" in the past month, and divide up your monthly payment amongst those pages (after taking their percentage).

On Flattr, I donate €2 per month. If I "thank" one page in a month, that page gets €2 (less 10%). If I "thank" a hundred pages in a month, each of them gets €0.02 (less 10%).

The "transaction cost" includes the human burden of remembering and typing a password. That seems to be enough to stop micropayments being used by most people.

The Flattr solution (pay a lump sum, which gets "used up" steadily over some months at your chosen rate, and "click freely" to allocate your donations) works really well. It's the only model I can think of that can work safely and effectively on a single click.

Yes, you put a Flattr button on each blog post, right next to the content. If people like the content, they click the "Flattr" button. It takes about the same effort as saying "Thanks".

If a person is concerned that all the Flattr payments in a given month are of an identical amount, they can use PayPal to make donations of whatever size they choose. But ask any site owner who has a "Donate" button on their site - very few people will donate. What Flattr changes is to make it so easy to donate that there's very little disincentive.

Fortunately that's not the case with Flattr, and I wouldn't use Flattr if it worked that way.

You initiate a payment from PayPal to Flattr, for an amount of your choosing (say €20). Then you tell Flattr how to use that money (e.g. €2 each month). When your payment runs out, your Flattring stops unless you choose to initiate a new payment to Flattr. At no time is there any kind of automated or Flattr-initiated withdrawal from your PayPal.

Incidentally I'm Flattring €2 per month, and earning about €3 per month from Flattrs. I would love to Flattr with BTC instead if the Flattr guys would offer that option.

Currently the Flattr user bears the cost of the PayPal transaction. But all of your other points I agree with.

As usual, noagendamarket is quick off the mark. Here's his forum post at Flattr where he suggests allowing Flattr accounts to be funded with bitcoin. Please everyone register and reply:
http://forum.flattr.net/showthread.php?tid=550