I work overnights, where I am mostly in an office, parked infront of a computer. I’m sure my fellow dopers have loads of good links for me to waste time at 
Oh, and I should mention there are webfilters on this computer, so most games are gonna be out.
How about YouTube? It may not be up your alley, but I’ve just wasted an hour watching songs from Disney movies from my childhood.
At home, yes. But I can’t view anything with sound. YouTube is an excellent timewaster indeed!
Best time waster ever. I have lost many a would-have-been-productive evening to it. If you’re not familiar with it, it’s a wiki about the various literary devices (tropes) found in television, film, literature, video games, and so on. It describes them in detail, picks them apart, pokes them with a pointy stick, and provides memorable examples from our collective entertainment culture.
Just stick your favorite book, movie, TV show, video game, webcomic, or what-have-you into the search box and start reading. Be careful, though – before you know it you’ll have clicked all the way from Star Wars to Seinfeld with a million other pages in between (like Rubber Forehead Aliens and I Hate You, Vampire Dad), and it’ll be three in the morning. 
chat with a stranger
I’ve collected a bunch of other links here:
Do you like online games? I spent last summer using up precious weeks of my life playing the tower defense game Gemcraft. This summer, it’s Gemcraft 0: Gem of Eternity. You can find them on Armor Games, and all your free time will fly right by.
Lileks.com, particularly the Institute of Official Cheer. I can spend hours just poking around the Gallery of Regrettable Food and the Gobbler site, and there’s plenty more as well.