I make the Amazon virtual machine images that I used to build the Windows and Linux binaries available... but Amazon recently took them down because they contain my ssh public key in the "allowed to login without a password" file. Removing the public key and then making the modified virtual machines public again is on my TODO list (Amazon doesn't want anybody to have a 'back door' into a public machine image, and bravo to them for checking-- I had no intention of logging into other's bitcoin-build-environment virtual machines, I just needed an easy way to login while I was putting together the releases).
If you have an EC2 account, you can run them and recreate the exact build environment and check to make sure you get exactly the same executable code (the compilers may put timestamps inside the files which you'd have to ignore).
The plan for future releases is to use devrandom's 'gitian' build system, which is a spiffy way of creating a well-defined virtual machine image from signed and trusted repositories, fetching a specific version of the code from the git source tree, and compiling in a way that is completely reproducible.
See: https://github.com/devrandom/gitian-builder