I just watched the eight extant episodes of The Guild (YouTube channel), a (what is the right term for this? Webisode?) comedy series about the lives and times of gamers. Here’s the first episode:
If you’re a World of Warcraft player, you’ll get all the jokes. If you’re any other kind of gamer, you’re probably get 80% of the jokes (“You like my helm? It’s +5 Sexterity”). Everybody else might get half the jokes.
The performances range from decent to marginal, but that’s pretty standard for any pro-am type project. The main creative force and best actor is Felicia Day, who’s done a lot of work (she was on Buffy in the final season, though I can’t specifically recall who she played–one of the new crop o’ slayers, I suspect).
The conceit of offline and online lives colliding feels fresh, though, and the writing is occasionally witty. In any case, there are worse ways to spend about 40 minutes (eight episodes times about five minutes).
I think this is probably the first piece of fictional video that I’ve watched consistently on YouTube. Do you have a favourite web-only show?
DarrenBarefoot.com 
Check out Mr. Deity. It’s web only, but almost professional quality. They mention on the site that they want to turn it into a TV show, but it’s too controversially for that to ever happen.
Not only is it good, but it offers an RSS feed for me to watch the episodes; a must if you want me to remember to come back every 2 weeks.
Best if watched in order, so you know the characters and their interactions.
Check out DND PSA’s
http://www.youtube.com/user/CreativeJuices7
Of course it helps to be a DND geek to understand it.