I'd say Rondo and Nate Robinson are the two fastest players in the NBA. The only competitors are Aaron Brooks and Monta Ellis.
I can think of a few other fast players but most of them aren't as fast or have lost their speed over age...
Iverson, Parker, Barbosa, Harris, Rose, CP3, DWade, LeBron, T.J. Ford.
I'm sure I missed a few!
Maybe Mike Sweetney.