For example, are there drop-in examples for common web-app frameworks? Would it involve the customer cutting & pasting a few long BTC strings between the browser and some separate wallet app?
Would the web-app keep polling a separate Bitcoin service to achieve confirmation/confidence that a payment has gone through?
1. A user clicks on a link to buy an item
2. Web application generates a new bitcoin address. This can be done by sending a command to the official BitCoin daemon, or by calling a method on the BitCoinJ Java library.
3. The web application asks the user to send a sum of money to the recently generated address. If the user is using the official Bitcoin client, they'd do this by clicking "Send Coins", then copy-pasting the address and the correct amount of money into the dialog box.
4. The web application then either polls the Bitcoin daemon to see if the transaction has come through yet, or sets up an event handler if the web app is using BitcoinJ. The transaction must obviously be sent to the right address with the right amount of bitcoins.
5. When the transaction has come through, you can now deliver the product to the user. If there's no particular hurry, or if the product is high-value, you may want to wait until a certain number of Bitcoin nodes have confirmed the transaction.
As far as I'm aware, there aren't yet any drop-in plugins for common web frameworks, but it wouldn't be hard to make one.
For instance, there could be a link like:
bitcoin://1MvtfpuCtfDb2EfbevDB1Ep6Z2X1h5nskf?amount=10.00
However, this is just an example, and nothing like this has been implemented yet to my knowledge.