I couldn't find another, though with gog's search who knows ;)

I updated the OP with some extra codes that I know came from bundles / IGS, but I don't have the expiration dates. I marked them as assumed expired, but if anyone knows the true answer please tell me.

Indeed. Codes for The Real Texas, Unmechanical, Pid and Waking Mars have expired.

I am so bummed. -4 to GoG.

I've asked devs for replacements, as per distributor policy, and so far the Unmechanical and Pid devs have kindly given me Steam keys.

The Waking Mars dev has run into trouble generating a new GoG code, but is willing to request another while being kind enough to offer a Steam key.

The Real Texas dev has offered to request a new code from GoG. Such a nice dude--he didn't even know they expire.

Time to hit the community wishlist.

Sorry to hear you had so many expire on you, but glad to hear the devs are willing to help out. And thanks for bringing Unmechanical to my attention.

What is the wishlist entry for? I'm sure others would be willing to vote if they agree.

some of those PS3 expired DLCs still work with no issues.
i had a God of War collection code to unlock some titles digitally, but never went online so didnt bother.
by the time i got around to finally going online i noticed the same deal, but tried anyways. had some success.

my expired ps+ code that came with the system however did not function as a free trial but instead as a trial against my patience. (had no clue there was even an expiration date, finally tried it out when it was an 'interesting' month deals and "freebies" -wise)

Shadowgrounds in Groupees Build a Meridian 4 Bundle (May, 2013) also had GOG key, unfortunately I can't give you expiration date, since already redeemed it (but most likely expired anyway).
(And of course, I forgot to redeem Unmechanical...)

Thanks I'll add it to the list.

Added two Humble Bundle gog keys thanks to Grargar

I thought codes weren't supposed to expire (unless the server gets replaced).

Is it only Groupees codes that die?

Hmmm same here, however when i entered the code on PSN i still got what was promised... (Alice in wonderland: madness returns) I guess they can't guarantee the code after a certain date, but...

I don't know...

well its been a hit or miss the batman ps3 game i bought on retail was suppose to have a voucher for animated movie but the code had expired , contacted wb support and they said they cant do anything since the code redeem time was up

Hmm I missed those I suppose :) Thanks for pointing them out. And thanks for adding another key to the list.

Added Defender's Quest from latest Humble Weekly. It expires soon, so if you have it use it.

Oh, wow. Is that the first time HB has offered a GOG key?

Are you sure?
I got the code today and it would have had expired on that date, but perhaps one could get the GOG code later.