Choice Privileges, the frequest guest program of a variety of low-end hotels (sometimes Comfort Inn is just the only decent place in some towns, but I’ll still pass on EconoLodge) has a member referral program — new members referred by an existing member get 500 bonus points on their first stay, and the existing member gets 500 points as well.
Thanks for Free Frequent Flyer Miles for the pointer, and if you’d like a referral for the bonus points just email me.