Choose your favorite from here: http://sourceforge.net/projects/bitcoin/files%2FBitcoin/
You've got to be careful. The fee isn't 'imposed' to harm you. If you send without a fee when the current version wants it other nodes may consider your tx to be spam and not forward it.
The current vanilla client doesn't refuse to forward the transaction, but most miners are not going to include the transaction until it's old enough to qualify as a free transaction. I believe that the current client defaults to a transaction fee, but that can be changed in the settings. The vanilla client will refuse to create a transaction based upon an input transaction that is newer than 6 confirmations old.
Oh, my bad. I was sure that it was the others won't forward it. So a modified client can flood the network? Everyone will forward? Reference to a thread about the current state of this would be much appreciated.