If you hover over the My Gaia tab, under Other Stuff your Achievements will be the 5th link down.
If you have the GaiaUpgrade extension it is still inside the My Gaia tab but it might be in a different position.
Rul
I don't think I have any super weird achievements but there are some interesting ones that are Available like: Sausage Fest and Clambake where 15 male or female avatars post on the same page. Toothfairy is gift buckteeth to someone wearing wings.
Stuff like that! What shows up under Available Achievements for you?