Do you like to roleplay? MTS has an online play-by-post Roleplaying Forum, for all sorts of interesting RP themes (many non-sim-related) - write collaborative stories with other people for fun!
Just installed the Sims 3 patch or about to? Read this article for helpful advice about patching and keeping your custom content working!
A group for people interested in 3D modeling of anything (not necesarily Sims 2) to learn about, get feedback on, give feedback on, and enjoy looking at pretty meshes. =D