Tools to help edit / navigate / hack the Kernel source:
Downloading
If you want to download the lastest kernel source, you need git. You can get it from [http://git.or.cz/index.html here].
There is a very good tutorial for kernel hackers on git [http://linux.yyz.us/git-howto.html here]
Navigation Aid
[http://lxr.linux.no/ Cross-Referencing Linux] : Nice website to browse the kernel source, search for identifiers, and diff between kernel versions. Uses [http://sourceforge.net/projects/lxr/ lxr] as its backend.
[http://www.kernelhq.org/ KernelHQ] : Another website to browse/navigate the kernel source. Has all the kernel sources since 1.0.
Navigation Utilities
[http://ctags.sourceforge.net/ ctags]
[http://cscope.sourceforge.net/ cscope]. Tutorials: [http://cscope.sourceforge.net/large_projects.html Using with large projects], [http://cscope.sourceforge.net/cscope_vim_tutorial.html Using Cscope with Vim].
Version Control
Navigate the changesets applied to: