you can use google analytics to track exit links... just ad this bit of javascript to your outbound links...
Code:
onClick="javascript:urchinTracker ('/name/of/your/link');"
what I do is then give it a name like /affil_program/tour and /affil_program/join and /affil_program/join2 etc....
then when someone clicks an outbound link, it will show up in your analytics report as the link you specified in the java script...
You can customize this as much as you want to keep track of where the link was and where its going, etc...
Analytics does have its downside though.. Personally I think it takes far to long to report, but for a free program, it is top notch.
We're getting ready to start testing webtrends and our stats program... I'm not sure how much better it will be, but it does give real time stats which is a big plus. The downside? It needs it's own server and is windows based....