xkcd cartoon: My Profanity Usage by Cause, link from DoctorOak Alex (I think). Replace "Mario Kart" with "Zelda" and you have me ;)
Left-Handed Toons (by right-handed people): An Open Letter to Subway, linked by booklectic. I also want to see bands called Unnecessary Dairy Overlap.
Cephalopod Surprise by Skippy, linked by j00j. If you've wondered why people suddenly have usericons declaring "Pie Doesn't Have Tentacles!", this is the context.
Harry Potter and the Deathly Hallows, condensed by mollyringwraith.
I may just have to rent/watch Music & Lyrics. This video is probably the funniest 80s pop spoof I've ever seen. Linked by rmjwell.
Livejournal entries with YouTube embedded videos by other people:
Have you ever wondered about the source of the /dance emotes in World of Warcraft?, linked by xiphias.
Xbox 360: The Red Ring of Death, linked by epi_lj. Hilariously funny "death metal" video. Well, hilarious if you know the context of the Red Ring of Death, anyway. Unless your Xbox 360 blew up that way.
Video of a little yellow dancing robot. WAAAANT! *dead of cute*
Actual Useful Content(!):
The Ikea Hacker, link from okoshun. How to reassemble Ikea furniture in different configurations than Ikea was originally intending and create new and interesting works of art (or storage solutions). Awesome :)