I saw this collection of mostly vintage-looking graphics w/ witty captions & thought it was pretty funny. It's not really "haha" funny but I find them amusing.
I liked this one - a good take on how much designers rely on computer technology nowadays:
The idea of adding funniness to generic graphic art is also the basis for the site of funny e-cards called Someecards.com. I've sent & received some of the gems on this site.
Combining these simple elements in the right way has a surprisingly comedic effect.