There is a great open source renderfarm manager available at www.cgru.info. We started using it at our studio (www.breitbild-vfx.com) a few weeks ago. Works flawlessly. Aside from Blender, it also supports After Effects, Houdini, Max and some more.
Setup is hassle-free, and you don't need any webserver, database or similar stuff running. Current version is 1.7, a major overhaul (2.0) is currently in the making. Load-balancing, rendernode management, job queue, priorities, job dependencies, you name it - it's all there.
If need be, just poke me here in the comments or over on Twitter (@tobkum), and I'll do a step-by-step setup description.
