There are very few exchanges and even few banks. Some of them have gotten hacked, mostly because of very weak authentication schemes. There's definitely a need for more financial services. Even if BitCoin (BTC) falls apart (liquidity goes to zero), other currencies can show up. There will most likely continue to be demand for a currency with no central authority.
TODO: How does Linden Dollars, Dwollah, work?
The only information kept secret is information about customers that can identify them beyond their customer identifiers (random numbers).
BTC, etc. bank (store wallets so they can't be lost, stolen, hacked, etc), possibly with interest
Exchange (p2p exchange between different currencies like usd<>btc, linden<>dwollah, ...)
Escrow (fair transactions between parties who don't trust eachother. One currency is held in bank while the other is confirmed)
Securded loans (customer has USD in account and wishes to lend another currency)
Exchange arbitrage bot (we give prices on our own exchange with a comission to keep it liquid, but get no priority over other trades)
?CFD market (spread betting on currency changes... or anything else)
Credit ratings (verified customers (gpg or something) get ratings based on paying back loans, making trades, ....)
API's to everything (allow bots, but might have to charge a small fee for each API call to keep costs down)
Host everything on github, etc. If you have nothing to hide, customers wont be concerned about getting screwd over.