BleepingComputer.com: control internet activity on network

Anyone have a recommended program to monitor and filter internet activity ?

1. I would like to allow some specific sites all the time and block others.
2. thunderbird and googletalk and various programs allowed but other others blocked
3.Only certain hours access allowed (full access for a short time span if possible)
Monitoring (log) would be a plus
I would like the above to be controlled globally via a server . And then custom settings per client ...All on one dashboard
If not possible per client settings would be ok ,, as in standalone,,
Not all clients will have the same accessability and restrictions
This is in a business enviroment

Am looking at CyberSieve and workExaminer .
Does anyone have experience with any of these?
Am leaning towards CyperSieve because of user friendliness.

Try DeepFreeze

It look great but Deep Freeze seems to have a lot of xtras i do not want to deal with . I only want to control internet activity . Am still checkin it out though , Thanks for the help