www.reddit.com. Subreddits of interests when bored:
www.reddit.com/r/funny,
www.reddit.com/r/gifs,
www.reddit.com/r/morbidreality (nsfw, discuss the darkest parts of our world, often disturbing pics) and
www.reddit.com/r/TIL (TIL is short for Today I learned, people post a lot of random facts they just found out with links to sources etc.). There's more subreddits out there that is worth taking a look at as well, just look around. Each thread mostly got NSFW tags on them if you don't want to be surprised by disgusting shit.
I'd also advice you to install the reddit enhancement suit plug-in (
http://redditenhancementsuite.com/) before browing reddit. It makes it easier to view images and browsing reddit in general.
Beside of reddit there's always Steam. Download it if you don't already have it. A lot of great free games can be found there along with Team Fortress 2 and Trackmania Nations.