The rules for Powers Monopoly were floating around the internet for a while, but seem to have disappeared. My copy of the rules credits Scott Weiss and Rick Rubenstein, but if that's an error please correct me. I think the only other place hosting it is Game Central Station.
All of the rules are the same as in regular Monopoly with the following exceptions:
1. Each player is given two powers assigned at random from the list below. Write each on an index card, or simply print the list and cut them into individual slips of paper, one per power. Then and have each player draw two from the pile. The powers give players unique abilities that allow them to subvert the normal rules in some way. Some powers require a marker to denote when they can be used (for example, once per trip around the board.) Use whatever you have handy.
2. A player may not use his powers while in Jail.
3. When a player lands on Free Parking, he or she receives a Zap (use whatever markers are convenient; just make sure they're different from power-specific markers.) The Zap may be played on any player attempting to use a power, thereby cancelling the power's effect. The Zapped player may not attempt to reuse any of his or her powers until the next player's turn.
As an optional rule, you can allow players to trade powers as part of a deal.
You can find the individual powers after the jump.