Dr. Horrible's Sing-Along Blog
If you like NPH who plays Barney in How I Met Your Mother or a slightly twisty version of himself in The Harold ^ Kumar flicks check this online musical out.
There's also Natahn Fillion who has been in Buffy, Firefly and it's movie Serenity, Drive and Waitress.
Then there's also Felicia Day who has that YouTube show called Th Guild and she was on Buffy as a Potential Slayer in the last season.
And It's written by Joss Whedon, his brothers Zack and Jed along with Jed's fiancee, Maruissa Tancharoen.