Here are the top stable coins as of today 5-16-18
Tether $2.3 b fiat backing
Dai $35m - from makerdao backed by ether
Sbd $32m backed by steem
True USD $14m - not sure but think it’s backed by fiat
BitUSD $14m backed by Bitshares
Nubits $4.5m backed by fiat
Corion $1.2m on etc chain backed by monetary policy
Basecoin, eusd (haven) and now circle coming soon! The race is wide open!
Check out cryptoslate.com for a nice summary of current prices. Incidentally we should get steem dollars on here.