Tools to help edit / navigate / hack the Kernel source:
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] is at the 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] (check out the tutorials: [http://cscope.sourceforge.net/large_projects.html Using Cscope on large projects (example: the Linux kernel)] and [http://cscope.sourceforge.net/cscope_vim_tutorial.html Using Cscope with Vim])
Version Control
Navigate the changesets applied to:
[http://linux.bkbits.net:8080/linux-2.4 linux-2.4]
[http://linux.bkbits.net:8080/linux-2.6 linux-2.6]
[http://mmlinux.bkbits.net:8080/main 2.6-mm]