I have made a slight modification to the EC2BuildSlave.
It now requires some additional input, because I had been hardcoding some values in, and thats sloppy, so I corrected it to allow you to put any variable parameters in the config file.
Basically, you will lay out a new EC2BuildSlave like this:

   from buildbot.EC2BuildSlave import EC2BuildSlave   c['slaves'] = [EC2BuildSlave("bot1name", "bot1passwd", "public key", "private key", "dns", "instance-id")]

   //Where dns = www.whatever.com:8898, or 88.123.55.456:8898

//and public/private key is your public/private key from Amazon

//and instance-id is the instance you would like to launch ("ami-87d530ee")

How, you might ask, does the DNS for your BuildMaster get sent to the new EC2 instance, and at startup no less?

Well, thanks to Ted (luser) Mielczarek, I now know about EC2 metadata. The DNS is uploaded to the new EC2 instance as a peice of metadata at runtime, which the instance can use in it’s startup scripts to start a BuildSlave pointed right at your machine.

Downloads? Sure, just follow the link.