Check them out here:
http://www.creativecrash.com/maya/downloads/applications/render-managers/c/
I've used all sorts of, but mostly smedge, lemon and royal render.
Lemon is too old now.
Smedge and Royal render are quite good, give them a shot.
Royal render is very simple to install and use.
Find it at royalrender.de
Also I would recomend Deadline, since supports a lot of maya and other software.
Made by prime focus (was Frantic Films).
If you have small shop, I would suggest off the shelf software, otherwise it makes sense to use some open source and change to requirements.
Als
