I just created three-signature wallet, which can be useful for pre-ico for example.
There are 3 founders, provided in wallet constructor, who can manage ETH funds.
Wallet can store any amount of ETHers, and any founder can propose transaction, which needs to be approved by one of another founders.
Transaction is always sending 100% ETH balance to specified address.
This is wallet which needs 2 signers of 3 available.
Source code of wallet is on github.