Allright! Two (big) online games I play are Nationstates (link in sig) an Ogame (
www.ogame.org). Have been playing NS for more than 2,5 years now and I love it. It's essentially a politics game where you create a nation and decide on daily issues. Besides that, there's a UN you can become a member of to vot on its resolutions and there's regions you can move your nation to and from. The issue-answering gets boring pretty quickly but its the region thing that does it for me and keeps me there.
I've been in my home region, Equilism, for almost the entire time I play. The region has its own forum where we deal with the governing of our region etc... We have a core group of active players and we've all become friends and stuff. I check it every day if I can and if I can't for a few days, I miss them.
The other, OGame, I've only been playing shortly. It's a space rts kinda game which I begun playing cause a friend asked me to account-sit while he's away on excavation. I liked it and created my own account as well.