Offshore clicks has a very good dialer. They teamed up with Varadox. (dialerheaven)
The newest version fully complies with UK, US and German regulations.
They just added a new feature to the dialer where if someone downloads it and decides to click the cancel button, it will redirect them to a page of your choosing. I find having this send them to a join4free full page ad is a very good technique.
http://php.offshoreclicks.com/cgi-bin/ref.cgi?evildick