Domain redirect is the best way and its completely Free. You can use affiliate cloaking software too but I think you have to pay. If you have no problem with URL shortening then go for it --> http://tinyurl.com/
You can find the related threads here. There are tons of threads related to how to hide affiliate link.
One easy way is to make a php file with a redirect in it and then call it something like /recommends/clickbankproduct.php
I use the php redirect method, but now CB offers this link shield thing - I suppose that's affective.
Don't use tinyurl for affiliate links if the site goes down your links will not work! I find it easy to set them up using a 301 redirect using .htaccess If you have to change the link, you only need to do it from one location and the links don't look like affiliate links.
URL shortening service or redirect, it is easy Why you want hide aff link? Do you think BFU can see it?
You can use http://moveto.ws/ - specifically designed for affiliates, it's completely integrated in http://cb-analytics.com too. It processes millions of hops by affiliates and it's yet to have any downtime.