Microsoft has just dropped the price on a number of their games. The titles that were discounted were

$19.99 (Formerly $19.99)
Midtown Madness 3 (Ebgames, Gamestop)
Voodoo Vince (Ebgames, Gamestop)
Grabbed By The Ghoulies (Ebgames, Gamestop)

$29.99 (formerly $49.99)
NFL Fever 2004 (Ebgames, Gamestop)
Amped 2 (Ebgames, Gamestop)
Top Spin (Ebgames, Gamestop)
Inside Drive 2004 (Ebgames, Gamestop)
NHL Rivals 2004 (Ebgames, Gamestop)
Links 2004 (Ebgames, Gamestop)

As shown above, Ebgames and Gamestop are already offering them at the new prices, other stores should follow within the next few days.