I would want to force bitcoind to include a specific transaction as an input of another transaction. This is so as to prevent people front wanting to launch a double-spend attack on the website. The method is similar to the one used by SatoshiDice. How can I accomplish this task with the standard client?
This will be possible using the 'raw transaction interface' that was added recently and scheduled to be part of the 0.7.0 release.
listunspent you can request a list of available coins sent to a particular (wallet) address, and with
createrawtransaction you can build a transaction that consumes specified coins. Finally,
sendrawtransaction can be used to broadcast a prepared raw transaction to the network.