Day 9 is great, and Tastosis (Artosis and Tasteless who's Day 9's brother) cast GSL - (Korean tournament, best players in the world) they're pretty funny, very high hame knowledge. gomtv.net is the website, starts 8pm week nights and some Saturdays. Sometimes casted by others with terrible humour but okay knowledge.
Rotterdam who casts for ESLtv in Germany (casts in English though) is one of my favourites he's just a really cool chill guy, he plays non competitively but he's ranked very high and has very good game knowledge.
Husky is awesome, he's come a hell of a long way from when he started, HD is less entertaining but has slightly better knowledge, Doa is alright on youtube (dumb jokes during GSL).
Also next MLG (biggest tourney in America) is next weekend iirc, casted by Day9 and Husky + Tastosis
On teamliquid.net there will be featured streams of pros and tournaments going on as well as a bunch of randoms, you can learn a lot from these.