If you don't have the big bucks to spend, I find that a vise and a 4 1/2 angle grinder is the best way to go. With practice you can keep your ground edge straight w/no problem. There's also pics of a home made setup here that looks really good. (If my memory's right, the builder even included specs on how to make it). It's made using an angle grinder (what we refer to as a "side grinder") and plywood. I don't have the link but look around here and you'll find it.