So blatantly taking stuff from another blog here (found on the very good cosmicvariance which I keep plugging - read it for it is good), but I enjoyed it so I though I'd spread the joy. From this post there are some great cartoons/comic strips taken from this website - take a look at it and laugh. Here's a couple that were posted on cosmicvariance:
And here's a few I saw just looking at xkcd that I liked - there are some far more funny ones on the website though - I'm sitting at the back of my conference pissing myself whilst looking at them:
And for the truely geeky:
Definitely have a look.