I've made public the windows, linux32 and linux64 Amazon Machine Images used to build bitcoin 0.3.20. If you have an Amazon EC2 account, you can launch them and have your own working build environment for linux or windows bitcoin (paid for by the hour).
They are:
ami-4adf2c23 32-bit Linux (Ubuntu 9.04)
ami-12df2c7b 64-bit Linux (Ubuntu 9.04)
ami-7a21d213 Windows (with MinGW)
All created in the us-east-1b zone (I don't know if Amazon automatically migrates public AMIs across the world).
After launching the Linux VMs, you login as root (using the ssh keypair you specify when you launch).
After launching the Windows VM, you connect via Remote Desktop and then login as Administrator, password "bitcoin development" (you should change that for your instance as soon as you login, of course).
They contain bitcoin, bitcoind, and everything needed to build them, already built. You could launch instances and try to generate coins, but that's not cost-effective.
(Updated 22 Feb with 0.3.20.01 Windows AMI)