The main rational that I have for this, is that at the moment it is inconvenient to write a bitcoin address by hand... or even type a 32 character address by hand is annoying... It would be much easier, say by SMS to just message say a 5 charter one.

This is a simple project to have a bit.ly style URL shortener for your bitcoin address....  all it needs to provide the full address in plane text.  On account of this usernames reputation.

Longer-term: an API so that the shortened address may be used directly with the bitcoin application.
(Implementation for a private hash for security)   e.g. bitcoinaddress.com/A4IN (Z5 35 Up)  the Z5 part is private and applications can use it to check if the returned address is correct.  Because desired addresses are hard to generate, Prob a six digit base 58 will suffice.

Even Longer-term: a implementation of a Bitcoin DNS style system. (with security)

Any Ideas/Comments??

question, is there a check hash built into the bitcoin address?

[Edit 1] - changed the hash check part... was very vulnerable to an rainbow address table.  38 billion seems like a good balance, have in the API an optional 8, 10, and so on charter checks.

[Edit 2] - changed the bounty... 200 BTC was way more BTC than I have spare.