I like CollegeHumor.com. Even though the website title is missing a letter, I find it's a good site to visit on a daily basis to find stuff like this. There are some genuinely brilliant and original short fims that range from Minesweeper: The Movie to the ongoing Street Fighter: The Later Years series.
I recently came across a series of pranks that two website staff members have played on each other in the last few months. It starts off fairly simple but effectively but then the shit kicks off towards the latter pranks. It's painful to watch but that might be what makes it so good.
Watch all of them here. I'd advise starting at number one.