50 is as short as I'll ever shoot people with on a crop body except for very specific situations. I was able to shoot two large guys with a large prop in a relatively cramped hall a few days ago and get ample framing with my 50. For most situations 85 is probably a pretty good bet.
The Rokinon/Bower/Vivitar/Pro Optic/whatever 85 1.4 is a pretty interesting option. It's manual focus but incredibly sharp and costs about $300. I was playing with one earlier today and was pretty impressed.