Ask HN: Great startups with affiliate programs?

We're selling some ads on our blog but we don't want empty slots, so we're going to be using affiliate programs to fill any inventory we don't sell. We want to promote companies we know and trust, so if you have a product you're proud of and an affiliate program, please let us know.

Note: The slots are 125x125, so ideally you either already have banners in that size or don't mind if we create one.