Linux's memory requirements are actually quite modest. Still if you have four megabytes or less or you have eight megabytes or less and run X, you should look closely at these tips. If you are running the kernel that shipped with your installation distribution, shame on you. It probably has lots of features that you don't use.
Kernel memory is unpageable.
IPX may be safely disabled. Statically linked programs eat memory. If you have programs that you use often or that are large that are linked statically, rebuild them with dynamic linking. This will save the file in the root directory. Then edit the destination file.