PoS = proof of stake, rather than mining by finding hard hashes, transaction fees are distributed to nodes running the code proportional to stake (i.e., number of coins).

I'd suggest looking into bitshares, a PoS coin that doesn't simply assign transaction fees proportional to stake, but assign them to "delegates" elected by the stake holders. These delegates only keep a fraction for themselves and destroy the rest, which creates value for all other shareholders. Since it is a market, the fraction delegates keep to themselves will approach the cost of maintaining servers + whatever value add they do for the community (run faucets, developer time, hosting community services). Thus, it is an efficient (in energy) and robust system (from attacks) since assigning block production to delegates protects against many forms of attacks, you can read more in the DPOS white papers.

Bitshares is also a flexible platform for providing services beyond just "coins." It's more of a technology base than a product in itself. The first product is a distributed exchange where users can generate their own securities to trade, the next version will be an exchange to trade contracts pegged to assets (USD, gold, BTC), a long with plans for DNS, lotteries, music/literature publication, etc.