Anything goes really. Games for games, games for money, etc.Just post your offer (what you're looking for/what you have) and you can deal with people through PMs.
Also, check here for known scammers:
http://www.gog.com/forum/general/known_scammers/post1

Thank you for your reply DarkoD13. Anyone looking to trade their games for money please pm me. Open for any kind of game as long it is good. But really low on budget so would prefer low cost games in range of 1$-3$ ( I know pathetically low). So if anyone looking to get rid of their unwanted games or played games, Will pay by Paypal. please contact.

Cheers..

...

...

Have: Supreme Ruler: Cold War (steam gift)

Want: Offers

Can you offer cards here? I have a duplicate card, and I would like to trade it for another.

Try here - https://secure.gog.com/forum/general/the_steam_trading_cards_topic

Thanks, will do :D

WANT:

Risen 2 and it's DLC.

HAVE:

http://www.gog.com/forum/general/classifieds/post2898

i don't see why not most cards are worth more than the bundle fodder offered here.
lol was going to suggest making another post for cards.
thanks

closed

Highly Interested in Mount&Blade Warband + Napoleonic Wars or Mount & Blade Collection, I know it's pricey, therefore you should bare in mind that several games from my list will be yours if we work the trade out :)

[Have]

Desura:

- Pirate Hell
- Enola
- Dungeon Prospector
- Grimind
- Reversion - The Meeting
- Ensign-1
- HyperSonic 4
- Zombies
- Eleusis
- Paranautical Activity
- Radical Roach
- Enamel

Steam:

- Red Orchestra Ostfront 41-45
- Red Orchestra 2 Heroes of Stalingrad
- Miner Wars Arena Special Edition
- Karateka
- Earth 2160
- Wasteland Angel
- Stellar Impact
- Trapped Dead
- Robin Hood: The Legend of Sherwood
- PAM + DLC (Post Apocalyptic Mayhem)
- Pacific Storm Allies
- Avencast: Rise of the Mage
- Chains
- Alan Wake
- Alan Wake's American Nightmare

Others:

- $50 Best Buy Gift Card Code

And of course feel free to make offers and ask any questions! (GOG, Desura, Steam, GG and Origin only)

Cheers!

Successfully traded with: DarkoD13; Momo1991; Giltonnam; Darthprymus; Suzaku-sama; alexkoti; Accatone and adambiser

Link to Have / Want / Wishlists: http://www.gog.com/forum/general/classifieds/post7129

I'm interested in trading my Desura and Steam Keys with games from the current Weekend Promo: http://www.gog.com/promo/adventures_weekend_promo_050713 where most games on it are interesting for me.

Done