Animal Jam Quest: Codes:

Here is a list of gem codes that are still valid, starting from the oldest.
All these are proven to work.

Possible gems you can earn right now: 1,100

Here is a list of inventory codes that are still valid, starting from the oldest.
All these are proven to work.

gecko -- lime green gecko plushie (Note: This code is currently having major glitches. You cannot receive the item, even if you press 'Accept'. Animal Jam has been notified of this.)

Here is a list of gem codes that have expired, starting from the oldest.
All these have been proven not to work.

Possible gems you could have earned: 22,700

Here is a list of inventory codes that have expired, starting from the oldest.

These are all the codes as of March 13, 2012.

From Wiki Answers

Animal Jam Quest