From Hard Drop - Tetris Wiki
Fan made online game.
 External Links
by Jürgen Müller - freeware for Windows, created with "GameMaker".
It has a very good single and multiplayer-Tetris, plus Breakris - Breakout and Tetris at the same time.
Play with Keyboard, Maus or Joystick
Multiplayer on Single-Computer, LAN or Online