How does one make multisignature transactions with the bitcoin client? With the release of bitcoin version 0.6.1rc2, it is now possible to do M-of-N required signature transactions in the main network. But how does one actually perform such a transaction?

I've been trying to piece together how to do this mostly from the BIP 11 and API calls list pages on https://en.bitcoin.it/wiki/

I guess you can use 'addmultisigaddress' call to bitcoind to add a multisignature address to your wallet and then send coins to that address. This is the part you set up, say, an escrow.

However, I can't find the bitcoind call to create a transaction for multiple signing or the call to sign such transaction.  In other words, how do you send coins from a multisignature address? How do you release the tied-up coins?
Bitcoin version 0.6.1 doesn't have useful multisignature support yet, either in the GUI or via the RPC interface, because there is no support for partially signing a multisignature transaction.

What is supported:  creating a multisignature transaction (using addmultisigaddress), and sending to a multisignature address (either your own or somebody else's).

Testing spending of multisignature transactions-- if all of the private keys required to spend a multisignature transaction are in the wallet, then those coins are added to the wallet's total bitcoin balance and that transaction will be spent if the normal coin-selection code decides to use them for a spending transaction.

Pull request 1456 adds low-level support in the RPC interface for multi-device/multi-person multisignature transactions.