Just wanted to share something I built, since threads like this are exactly what gave me the idea — a little site called Referral Robin (referralrobin.com). It's free to use, and the idea is fairness: codes rotate round so it's not always the same one or two people's links getting all the traffic while everyone else's sit unused. You can grab a code for whatever you're after, and if you've got one going spare (bank switch, energy, cashback, whatever), you can add yours too and it'll get its turn.
Not trying to spam the thread, just thought it might be useful for folks who post an offer here and then it gets buried on page 4!
Happy to answer any questions if people have them.
Www.referralrobin.com