Over on the Official Google Blog they have a posting about transferable stock options which they intend to implement soon.
From the posting:
Typically, employees get value from stock options by exercising them after vesting, and then selling the stock they get from the exercise at a higher price, provided the company’s stock price has appreciated since the time of grant. With the TSO program, employees will also be able to sell vested options to the highest-bidding financial institution, which may be willing to pay a premium above the difference between the exercise price and the market price for Google stock (even when the exercise price is higher than the market price). The premium paid is for the time value of the options.
Via Google Blog