You have a few options.
1) Cisco make an appliance they call the Cisco Director. I think it runs about $3500.
2) VA Linux makes and appliance based on, well, Linux. It comes loaded with the OS and all the required packages and soon they will have a nice little web based admin tool for it. I think its in the $3500 range as well.
3) You can use a software package called Ultramonkey. Ultramonkey is actually what runs the VA Linux appliance and VA Linux actually funds some of the Ultramonkey development. Ultramonkey is free to use but you still have to have the hardware to run it. You are probably looking at about $500-$700 depending on what kind of machine you want to run it on.
I can't really say too much about option 1 or 2. I've never used either of those appliances. I have used Ultramonkey on a machine I've put together.
**Warning: I am, by no means, and expert on this software.
Some of the how-to's are a little lean on the details but it actually not hard to configure. I'll be happy to answer any quesitons that I can. The Ultramonkey web site is www.ultramonkey.org