hiding affiliate links

I built a directory website and now I want to monetize it with affiliate links, but I don't want it to be obvious. Instead of just adding the link is there some tool (ideally free) that "hide" the links so they don't look like affiliate links. So instead of the link being something like...

Whats the best way to forward domains to an affiliate link. e..g. xyz.com points to http://jhjhjhjkjhjhjkk.com/?whateever Ideally I want to tweak keywords, description etc. Is there a script a piece of php or a good service to use? Thanks in advance