Restricting Access to the Internet

Recently we worked out a deal with our local ISP, we would house some of their equipment for free use of the T1 dropped in. It has worked great! Of course, with the click of a mouse our employees can spend hours upon hours surfing the net and we have noticed a significant drop off in production. I cant totally eliminate the use of the internet, because it has become vital to our success, however, I want to set time restrictions for internet uses. Im not as much concerned as where they go, but how long they spend on the sites. We have a basic peer to peer network, with 7 computers all running Win2k. Any solutions on how to solve my problem? We also have a couple of employees that are Tech Savey and I would like something that they would have a tough time trying to bypass.

We have a linksys router (BEFSR41). Another item I forgot to mention, we have certain websites that need to be checked frequently, can I configure it in such a way that the employees have unlimited access to these sites? Also, they would need to be able to use their office email without restrictions. Are these things possible using the router? How hard is it to set the router up for this?

I would doubt that your router would support as advanced configuration settings as this, but it may. Have a look in the manual. I'd be looking to use something like Microsoft ISA server, which may be too much for this setup. You may also be able to setup a Linux box with some router software, if you can find some software with everything you want (which you probably can).