I have an idea for you that was prompted by the thread about printing plastic cards with QR codes on them to use in offline exchanges or promoting Bitcoin.
I think it would be pretty easy to create a tab on your site that would take the QR codes, text and some background image supplied and lay them out in a card format for saving/printing.
It would just take an SVG object element that refers to the QR codes and text with <image> and <text> tags. I think I could work that out and give you some sample HTML/JS code if you would be interested. I have worked with SVG before and it works quite well in browsers, though how it could be embedded with JS I'm not 100% sure.
My thought was to right click and save the SVG graphic to print out as a 4"x6" photo since this would allow nice colour graphics and design work to shine. With a background image embed option some really nice card designs could be created that allowed embedding the QR codes right on your page. I could see a user contributed library as possible. (The private key would be a separate element so that it can be printed separately).
Another idea I had was to incorporate Shamir Secret sharing to break the private key into several QR codes for printing. You would need several QR codes to re-combine a usable private key. This might be on a "Multi-Key" tab perhaps.
Ahhh.... Brain food. I'll think about that.
I'm still thinking about the private key redeem at MtGox and how awesome that is. I can't even imagine all the possibilities
I find that Private Key formats can be a source of confusion. I found this article on the wiki:
https://en.bitcoin.it/wiki/Private_keyIt does not describe the "Standard Private Key" that MtGox defines as:
Standard Private Key: The private key must be 32 bytes encoded in base58
Also, MtGox has a secondary private key format labelled "SHA-256 Private Key (E.g. Casascius Coins)"
which appears to be the option if you want to redeem a private key in hex format (Mtgox accepted the 64 character 0-9 A-F sequence... I'm waiting to see if the deposit of BTC works). Also, Casascius Coins use a the mini-private key format.
So to use this option with a mini-private key you have to first SHA256(MiniPrivateKey). This is making me think I should create a tab to convert between different private key formats. I like just showing one private key format on bitaddress to keep things simple otherwise people might think they need both private keys and not realize the two private keys are equivalent and just being shown in a different format. Although, I'd rather contact MtGox and have them add the Sipa Wallet Import Format (WIF),
I had to do some manual JavaScript work to convert from WIF to HEX to redeem at MtGox.