So way back when the 3ds first came out, I got the Ambassador program along with my purchase of the game because of the price drop. At first it was all well and good I saw a ton of free retro games because of it and I got a few specialty Miis through MiiPlaza that my brother didn't get but with the new 3ds out I was just wondering what all of the benefits were for the Ambassador program.
According to Nintendo Wikia:
The Nintendo 3DS Ambassador Program offers ten NES games for early adopters and also offers ten Game Boy Advance games starting December 16, 2011, making twenty total.
In addition to the twenty free games, Nintendo 3DS Ambassadors may also download a special Ambassador Certificate. The certificate has a notifications feature, which when toggled 'On' allows the player to receive special notifications exclusive to Nintendo 3DS Ambassadors.
For the full list of 20 games, you can check here