http://a072-web.nyc.gov/inmatelookup/
From Bronx or ManhattanTake the number 4,5,or 2 train- #19 or #2 bus to 149th st. and Grand Concourse. Walk half block down 149th street toward Lincoln Hospital you can take the Rikers van from 149th and Anthony J Griffin Pl. The van will travel over the Rikers Island Bridge to the Rikers Island Visit Center call (718-568-5685)
Read more:
http://wiki.answers.com/Q/How_do_you_get_to_Riker's_Island#ixzz1CooGzZZ5