sQusi Tracking Plus
Full user review
"Great for blocking ads, adding security"
It blocks a lot of ads, and you can make it block even more. Since it can block specific sites, it also can add security to your system by preventing the download of viruses, etc from those site. Sites like MySpace can sometimes link to malware.
Sometimes it blocks a site or prevents the download of a file. It would be nice to have the option to see what was blocked, specifically, as you are browsing. Sometimes the install or reinstall is difficult because their registration setver is down
Bottom line is that it's a great program to keep running on your computer!