Play music mostly. I also have a tv tuner so I can watch tv but I tend not to.
I don't like gaming if it's late. I feel I need time in case I get really into it. Same with movies. If it's a 2 hour movie on a work night I know there will be other internet things I'll want to do so I'll end up going to bed late.
Digg, Reddit and Stumbleupon are a fall back but Digg and Reddit seem to be getting a bit boring lately.
I enjoy coming on here and reading my favourite posters even if they're posting about something I'm not interested in or knowledgeable about.
All this and my job. Bloody tragic really