They're p'bly all source - I don't think any are precompiled. But these:
ftp://ftp.kernel.org/pub/linux/kernel/
are p'bly what you're looking for. Enter the directory for the version you're looking for - i.e. if you want 2.6.12, enter the 2.6 directory. The .sign files are for checking that sort of thing, and the .tar.gz and .tar.bz2 files are the kernel sources. Grab the one you like better, they're the same thing only compressed different ways.
linux-2.6.11.11.tar.gz is a .tar.gz file of the 2.6.11.11 kernel sources...etc.
