web filter software

[khizrs]

we have a router hooked upto our network which is sharing the internet over 3 pcs, 1 pc is mine and the other 2 are for staff.

I need something that will restrict their internet usage to stop them using msn/external email/other off topic stuff.

I have been searching and many of the solutions are based around a proxy server, is there anything that isn't designed for a proxy server?

Thanks!