The folks at Team Reaverbot have just released a playable demo for their highly anticipated 25th anniversary fan-game. This build features the full Bio Man stage and a battle against Tarot Man. No word yet on when the full game will hit, but you can look forward to more demos in the near future.
You can download it directly from Team Reaverbot's site here. While you're at it, be sure to grab the game's soundtrack in NSF format!