One of the students put me onto something that is going to keep me amused during lunch hours for a while. It is called StumbleUpon, and it is an add-in for Firefox or IE which suggests funky web sites that you might be interested in. You assign a bunch of categories that you like and then press the Stumble! button. It then takes you somewhere you might find interesting. When you get there, you can rate what you see so that other people can find it later. Great fun and highly unproductive, in that I can see myself spending hours with this thing. Within minutes I had found this link. I'm sure there are thousands of others.
But if you want to use the interweb to improve your life productivity wise you should really take a look at del.ico.us. Stupid name not withstanding it is actually massively useful. Again, it installs buttons on your IE toolbar, but this time it lets you manage and tag web favourites that you find. When you find a site that you don't want to forget (perhaps one you Stumbled across) you press the "post to de.lico.us" button and it then lets you enter tags for the link. It also shows you a "cloud" of existing tags so that you can easily find related sites. Very useful. You can see my tags here.