We've used surfcontrol before with pretty decent luck. It lacks a lot on the categorized site blocking but the monitoring is quite decent and the reporting is easily modified with crystal reports

www.surfcontrol.com

of course, you should have a proxy set up, and naturally Squid with a few minor adjustments can do everything you need as well, team squid up with IPtables and you can set up a killer transparent proxy / network choke.

http://www.squid-cache.org/