The software package below is a good one. I think they are the original folks to do this sort of thing, and I know they've been around for quite some time.  Don't get freaked out when you go to their site, they like to make everyone panic.  There may be a window that shows folders that are on your hard drive, but don't worry about that, it's just a bit of fancy code that allows it to show on the web page when you are there.  I think they do it just to heighten your sense of paranoia. 

Anyway, this is the best one I could find. So if you're worried about other people seeing what you've been looking at, this is the program for you.