They will be in Players Handbook 3 next year.
The Monk is avaialble as playtest version via DDI, and one Psion build is released (not as playtest) in DDI, too.
Psions use power points to turn at-will powers in the equivalent of encounter powers but still have normal daily powers. Other Psionic classes - except the Monk - are supposed to work similar.
Monks have "Full Disciplines" as at-will and encounter powers, which means they have an attack power with an associated movement related power. In any round you use the encounter or at-will attack power, you can also use the move related power. Their "striker" feature is Flurry of Blows, which allows them to deal extra damage to a foe (which doesn't have to be the foe they just hit.)