EB has a deal right now through mid-november that you can trade in three games and get Madden 2005. Granted, there are exclusions (Sports titles and older games) but there's a few ways to take huge advantage of this.
Method 1) You've got a bunch of games to trade in. 3 of them are only worth $2 apiece, but aren't excluded. Get Madden with those 3 games, then trade Madden in for $20. $6 of trade-in has now become $20
Method 2) Buy three of the following games for $6 or less. Trade-in and you've now bought a brand new copy of Madden for $18.
Method 3) Do Method 2 twice, and send in the receipt to EA for a free 2005 sports title! They have their Buy 2 Get 1 Free deal going.
CHEAP NON-EXCLUDED TITLES (less than $6)
Cubix: Showdown (PS2)
Drug Wars (PS2)
Egg Mania (PS2)
ESPN MLS (PS2)
F1 Champsionship (PS2)
MLB: 2003 (PS2)
Outlaw Volleyball Red Hot (Xbox)
Outlaw Golf: 9 More Holes (Xbox)
Outlaw Golf: ????? (Xbox) the other title, forget the name
Robotech CE (PS2) (Not sure what the CE stands for)
Robotech CE (Xbox)
Whiteout (PS2)
Enjoy some cheap Madden goodness