Peercoin, for one, has a 1% annual growth rate forever, and is designed to be more energy-efficient over the long term because it relies partly on "proof-of-stake" instead of just proof of work. There are a couple other proof-of-stake currencies too, and some unimplemented ideas like proof-of-burn. Another interesting currency is Freicoin, which uses proof-of-work but has demurrage.