I like to check 3rd party binaries into a "lib" directory that contains any external dependencies. After all, you want to keep track of specific versions of those libraries right?
When I compile the binaries myself, I often check in a zipped up copy of the code along side the binaries. That makes it clear that the code is not there for compiling, manipulating, etc. I almost never need to go back and reference the zipped code, but a couple times it has been helpful.
