Lazy API
For the incredibly lazy and/or incompetent web developer, I present the lazy man's bitcoin API (copied from a forum post)
Problem: Lazy web designer (me) wants to use bitcoins without dealing with installing bitcoin on a server, installing a shopping card interface, or using ugly merchant services with callbacks.
Solution for sending bitcoins: Use the MtGox API (https://mtgox.com/support/tradeAPI)
Solution for receiving bitcoins: 1) Input a list of bitcoin receiving addresses to your database 2) Give a bitcoin address to a potential customer 3) Have the customer tell you when they have sent the coins and have at least 1 confirmation 4) Check blockexplorer to see if they sent the right amount (i.e. http://blockexplorer.com/address/19hMEAaRMbEhfSkeU4GT8mgSuyR4t4M6TH) 5) Wait for more blocks (confirmations) if paranoid 6) Give them what they paid for 7) After a reasonable amount of time has passed, you can re-use the address for another customer
You could avoid having a list of addresses and reusing them if one of the wallet services someday lets you get a new address via API call, but this will work for now.
Bad idea: Selling bars of gold this way (owner of blockexplorer.com could rip you off) Good(?) idea: Selling naked pictures of your grandma this way (owner of blockexplorer.com won't bother)