What I do is set up a directory called /go with a htaccess with the lines
Redirect /go/site.com
http://site.com'sverylongreferralcode
then I just have to put links to mysite.com/go/site.com
not only does it hide the referral link, it's easier to remember when I want to post it somewhere as well as allowing you to change the links all at once if the sponsor goes under