Quick note: Just Cause 2 is one of the games in the $20 trade-in promo towards recent releases, so I actually picked up a copy on 360 and PS3 (with store credit) for like $16 each and got $20 each credit for AC:Brotherhood.
My first tiny flip!
In addition to including pre-order bonuses until they run out, Amazon also tends to have a metric ton of Atlus pre-order bonuses. I recall buying Persona 4 almost a year after release, and Amazon included the pre-order art book.
I had a lot of trouble getting this to go through on the website, but I did end up getting Knights in the Nightmare PSP ($30) with Super Mario Galaxy 2 at 50% off ($18 after EDGE).
Some of the stuff I traded in today (8/21):
360:
Halo 3 - $5
Darksiders - $9
Wii:
Mario Kart wheel - $2.25
PS2:
MLB Power Pros 2008 - $1.50
DS:
Trauma Center: UTK - $2
Trauma Center: UTK 2 - $3 (these two may be switched, can't tell on the receipt)
Hooray!
Base (with 30% and EDGE)
5/1
Final Fantasy XIII (360) - $24.00 ($33.60)
Mario Kart (DS) - $10.50 (14.70)
All told, free 3D Dot Game Heroes with a little left over!