The 2.4-hf kernel tree which only contains hotfixes for 2.4 mainline kernels up to and including 2.4.32. These are intended for people who cannot upgrade for various reasons, and who still need to apply a security or stability fix. All patches in this directory are extracted from the next mainline release or pre-release, and I will try to keep up to date with official fixes. Newer kernels use a 4-dot notation to provide fixes in a stable official branch. Normally, you would only need stable mainline, but if for various reasons, you still need hotfixes for older releases, please ask me. You can link to this RSS feed if you want to be informed of updates. These patches are hosted on my employer's servers (EXOSEC) so that we can get a better bandwidth than I could provide at home. However, it is always possible that I get late at pushing updates onto the server, so if you think something is missing, it is possible that in fact I already merged them but not pushed the patch, or only at home. In this case, please ask me : firstname.lastname@example.org
The 2.4-wt tree, which is an overloaded kernel that I use on all my servers and stations, as well as some of my employer's servers because of some useful security addons it includes (PaX, Netfilter, Openswan, loop-AES, ACL, lm-sensors, ...). These are normally not recommended for inexperienced people as they might not be as stable as the standard kernel, and might require some tweaking.
Other directories contain various drivers and kernel sub-projects.