All of these samples are royalty free. There are 8 different drumkits. If you are after a way to sort your samples then read my post Sorting your Sample Library.
Drums samples are essential. These kits favour the electronic music genre, however I believe that any drum hit can be used in any style of tune! Infact mix your drum kits, layer different hits together on the same beat and see what you can come up with. Some of the songs that I create have three snares layered together all triggering at the same time. The trick here is to choose the right sounding samples and adjust the volume of each sample so that the overall volume is just right.
Experiment by layering different kicks, snares and even hats over the top of each other. What you will end up with is a fatter sounding and more interesting hit.