Other practical applications where I believe Bitcoin has serious value in ways existing payment systems just don't work or have large fees - that just haven't yet been realized:

1.  Getting around the restrictions imposed by banks, such as for gambling transactions even where they're legal.  (e.g. PokerStars offering bitcoin poker)
2.  Remittances (families sending money home to Mexico etc.), save on the hefty fees, assuming the BTC exchange rate can become stable.
3.  Anything a bank wire is good for (due to its relative irreversibility), without the bank wire fee.  (For example, buying gold and silver, or any other scenario where someone wires good money as a show of good faith as opposed to doing check/ACH/etc.)
4.  Anything Western Union is good for, without the Western Union fee.
5.  Anything where foreign exchange is a factor (such as import/export of wholesale goods... if you're going to be trading a foreign fiat currency, BTC is no more difficult).
6.  Pornography, both legal (e.g. someone who doesn't want to share their CC# or personal details with a porn site, such as for fear of getting persistently rebilled or receiving unwanted communication), and illegal (such as in countries where all porn is strictly forbidden)
7.  Online pharmacies, for same reason as #6
8.  As a way for citizens behind oppressive firewalls to buy themselves access to personal unpublished VPN services.  (e.g. instead of trying to GPU mine, any John Doe in USA can receive bitcoins out of thin air just for running something on his router that lets someone in China forward traffic off his IP).  This would be valuable because China can automatically block all the tor nodes, but can't really block every John Doe whose IP is privately given to a small number of paying customers in China.
9.  Sort of like #8... As a way for communications equipment to negotiate and buy communications services on an automated basis.  Example, a cell phone or internet access that can roam absolutely anywhere, because a client can pay its own way anywhere without need for any sort of agreement or reconciliation with a wireless carrier.  Services such as pay-as-you-go WiFi - where anyone can provide or consume services - would be possible.  This would be the over-the-air equivalent of shoving quarters in a pay phone.  A radio-frequency device could simply broadcast offers to pay X BTC for delivering message Y to recipient Z, and any device that understood the offer could accept it.
10.  Antispam stamps.  Put a Bitcoin private key in a message header, guaranteeing that the recipient can be paid for receiving it if he so chooses, and a server can whitelist the message on that basis alone.  If the recipient doesn't redeem the private key (e.g. they don't consider it spam), the sender can eventually take it back.

There are also some more illegal applications that I believe could drive the fundamentals behind Bitcoin even if I obviously can't condone them.  For example, bitcoin enables anonymous racketeering and extortion.  The sniper guy who ran around Washington DC a decade ago demanded funds on his VISA, if he could have demanded Bitcoins he would be far less traceable.  In addition, I seem to regularly read in the news about Internet cafes being busted as being gambling operations.  Bitcoin would enable plausible deniability for such operations, because a single internet cafe could sell bitcoins (or could send people across the street to buy bitcoins) and offer internet services where people are encouraged to gamble bitcoins at some preferred gambling website, without any provable link that the website has any relationship to the internet cafe.  Obviously I don't think that these things are good for the world, but they are something I consider inevitable in that the "cryptocurrency genie" is out of the bottle, and something I still consider reasonable to factor into my sense of what my bitcoins are worth in terms of what someone will pay for them.