URLFreeze

I really like this linkcloaker because first off it's free - which is a plus (there's also a paid upgraded version if I need to take advantage of it).  You can hide/cloak any affiliate link and track how many hits you get and where your traffic is coming from.  I also like the fact that even on the free version you can include titles & metatags which is a great SEO-search engine optimization tactic.  I highly recommend URLFreeze as a useful valuable tool for serious affiliate marketers.  Especially if you want to protect your comi$$ions!