All the episodes
All the episodes from both Season 1 and 2 and Shed.Mov, Dress.Mov and Apple.Mov: [link]Season 1
All the episodes in one video: [link]
Season 1 Blooper Reel: [link]Season 3
Nicole Oliver (voice actress for Princess Celestia and Cheerilee), Michelle Creber (voice actress for Apple Bloom and singing voice of Sweetie Belle) and Tara Strong (the voice of Twilight Sparkle) have confirmed that the third season is in production, will have at least 13 episodes.
Edit: A lot of the links were removed due to a copyright claim by Hasbro. So just use the "All the episodes" link for now.
Reposted so people can see episode 20. I did have a load of individual season 2 links up but I haven't had the time to re-add them all.