true, the 50mm f/1.8 is great (i have the 50mm f/1.4 myself), but you have to also keep in mind that the T2i is a crop sensor camera, meaning that the 50mm is going to act more like an 80mm, making it pretty tight and hard to film with if not on a tripod or very good with a glidecam. for a wider lens that will act like a 50mm, i suggest looking into the Sigma 30mm f/1.4.
I have Canon's 17-55mm f/2.8 lens, it's amazing. However, it's really expensive so another good one, as i believe kelsey suggested, is the tamron 18-55 f/2.8