The D&D class
In the 3rd Edition Psionics Handbook, published by Wizards of the Coast, the psion and the psychic warrior are introduced. These two psionic classes use the new rules and can be integrated into standard D&D games, at the discretion of the Dungeon Master.
The psion is a psionic specialist, as opposed to the psyhic warrior's blend of psionics and fighting. Psions specialize in one discipline of psionics, choosing from psychometabolism, psychoportation, psychokinesis, metacreativity, clairsentience, and telepathy. Psions are weak in combat, and function similarly to sorcerers in terms of game mechanics. The key difference is that psionics uses power points, as opposed to spell slots.
I highly recommend the Psionics Handbook to anybody who likes D&D. It seems much more balanced than previous versions, so it can be integrated fairly easily into existing campaigns.
The Psionics Handbook and D&D are published by Wizards of the Coast