EDIT: OK, there's no Gamecube section on the main menu at the top of the forums. Mods please move!!
Done
As for the individual prices of each, you could try looking at completed auctions on ebay for any game you suspect may still hold a decent value(I think some games such as Burnout2 for example still fetch a decent price).
Once you have a rough idea of how much you might get for them you could try popping them in the forum classified section here No fees so nothing to lose trying them there, the ones that don't sell I guess ebay would be your best bet.
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My opinions are my own & not representative of the AVForums