I only recently (as in like three days ago) started taking glutamine powder so I can't really comment on how good it is but I just bought a fairly inexpensive brand, Body Fortress. There aren't a lot of shopping options where I live but if I see any results from it I'll probably later look into shopping online for a wider selection. Good luck finding one that works for you, and I'll be following this post since I've been wondering about the same thing.

I use on essential amino energy. It also has caffiene in it so i use it mid day or during my workout. I hate going without it.