I'm trading in my DS phat, my GBA SP (I have my regular GBA to play older GameBoy titles with) and 30 (plus or minus 5) games/movies that I'll be trading in. I don't know how much I'll get for all of it, but I hope I don't have to pay ANYTHING for my Lite.
I'm keeping my GameCube. I'll need something to trade in when I purchase my Wii.