With the large number of pre-built kernels available these days, finding the correct one can often be difficult. With a few pointers, you should be able to figure out which kernel best suits your needs.
Most likely you will want to download one of the stable kernels. Unless you enjoy testing new features and "living life on the edge," the stable kernel will almost always be more than adequate for your system.
With the arrival of 2.2.18 and 2.4.0-test10, all of the changes in the Paulus and Ben kernels have been merged into the official tree. The Paulus and Ben trees are now frozen, and almost all of the PowerPC kernel work is done in the BitKeeper tree, or even upstream from that. In addition, the BitKeeper and Official trees will most likely be fairly similar to each other.
The default builds of the Official kernels are for the most part useless, at least on PowerMacs (iBook, PowerBook, G3, G4, G5, etc.). If you don't know where to start, we suggest you try one of the Official kernels built using pmac_defconfig, the default configuration file found in (source directory)/arch/ppc/configs. Official 2.6 PowerMac is a great place to start!