I am in far too many
xd Which groups I look at depends on my mood; I am a member of groups that appeal to my interests, but they fill my inbox
fast and I am not always in the mood for zombies/Pokemon/TF2 specifically.
I contribute art to those groups when I make art suitable for those groups. I go through phases with my art; sometimes Pokemon, sometimes Gaia, obscure videogames, My Little Pony, stamps, the infrequent emoticon or other pixeled work...
I currently run three Groups of my own
DMFAclub, a fanclub for an anthro webcomic
TAFponies, dedicated to a style of My Little Pony introduced in the first-generation toy line
HybridAnthro, because there are too many general-anthro groups and not enough focusing on particular species