I like GeeksandSundry, Felicia Day's channel. I don't know every show on there yet, but her six season webseries The Guild is awesome - especially for you RPG gamers out there! I'm no gamer but even I recognized a LOT of the geeky behavior that they did.
I also like Machinima. Not everything's free, but some series are, like Dragon Age: Redemption (also with Felicia Day), which is a cool fantasy series, based on the video game.
Third: "That girl with the costumes", AntiAiChan's very geeky channel. She's in her twenties I think, but she often makes me laugh, especially when she's really geeking out over some comics or cosplay.
Same goes for a related channel, G33ksoftheWeek. Five young geeky people who each vlog one day of the week. AntiAiChan has Monday, and I especially follow her. When I'm in the mood I watch some of the other's videos as well, but its mostly the Mondays that I'm interested in. Anyway, check it out and see for yourself.
Last but not least, if you want to watch some great comics art in the making, check out Nebezial1's Youtube channel. He's the artist on Ravine, the comic I'm reviewing in the upcoming listener created episode of the Spiritblade podcast. You can see him work, which is awesome!