I enjoy visiting this one from time to time: http://www.lovelylisting.com/. Mocks pictures from real estate listings.
Ha.
Lately, I’ve been wasting entirely too much time on Wolfgangs Vault, which has recordings of thousands of classic rock era live concerts.
The up side is that you can find listen to concerts as you’re working at your desk.
The down side is that once you get going through it, you will probably be doing a lot less work.
I thought this was it, really.
Though, MonkeyFilter isn’t bad, and some Dopers (I don’t know about you) would probably like sites like Pain In The English, or even Common Errors in English (I have wasted a lot of time there, mostly feeling smug because I already knew, but occasionally feeling very dumb.)
Oh, and undoubtedly the best (and truest) page on the whole Wold Wide Web. 
(It’s a quick hit, but you will return.)
AK Dog Doc’s Vet on the Edge. Life and times of an Alaskan vet. Good writing - Not so funny.
high-street DOT org
Cake Wrecks - professional cakes gone hilariously awry.
Awkward Family Photos - hilariously amusing family pictures.
Passive Aggressive Notes - Some of them are actually aggressive-aggressive. 
Arts & Letters Daily - always something good there to kill a few hours.
www.sporcle.com has quizzes on a wide variety of subjects. I particularly like the geography ones.
I watch quite a few tv shows, and I like to read Alan Sepinwall’s reviews. Sometimes, actors or other luminaries comment on his reviews.
Also, a guilty pleasure is Go Fug Yourself, a catalogue of celebrity fashion faux pas, with commentary.
http://plaidstallions.com/ this is a good one.
I’m very fond of the Comics Curmudgeon. Hilarious!
Oh, I forgot Shorpy - fascinating old photographs.
I like to eat, and I frequently eat out. I like perusing the site to pinpoint my next food outing.
Worth1000.com (photoshop contests)
And for online games, you can’t beat Gemcraft for timewasting. I started the Gemcraft sequel at the beginning of the summer, and I still haven’t finished it.