Why worry about hiding it...? Most of the people who you will care about that is on your sit, probably don't know whats an affiliate link.
If you just want to cover your affiliate link and clok it to one website, you might consider domain stealth forwarding where you can assign your url to automatically forward to your aff page from inside you domain control panel. I know go daddy offers this as a service, so does dynadot and probably most other real registrars. If you want to link from your current blog or website...then this current digital point member has actually created a free wordpress plugin to do it for you, you can find the link here: hxxp://forums.digitalpoint.com/showthread.php?t=1068257
thanks for that dead link insidethelab, that DP thread just points to a link with a dead blog and affiliate offers. Ban that dude
Use the below code to hide affiliate link <?php header("Location:http://your affiliate url"); ?> Code (markup): Save the above code to someting.php, then upload it to your site, say you upload to "go" folder, then yoursite.com/go/something.php is your hidden affiliate link.