If I have podcasts to listen to or just feel like playing something not too complicated. Bejeweled 3 and Spelunky comes to mind. Just turn them on, mute the TV, and just zone out for however long the podcasts are.
I play mostly on my own. I just recently started getting back into playing Battlefield 3 with my cousin and his friend and it's been 10x more fun then just playing on a silent squad. There was also the rare few times I teamed up with a co-worker in Borderlands.