Here's a rundown of the current badges and medals you can earn throughout the sites:

The Littlegrey Network:

Forum User - awarded for leaving at least 3 posts on the Littlegrey Network Forums in the past 30 days.
Forum Regular - awarded for leaving at least 30 posts on the Littlegrey Network Forums in the past 30 days.
Forum Fruitcake - awarded for leaving at least 120 posts on the Littlegrey Network Forums in the past 30 days.

The forum badges that appear under your avatar may take up to 24 hours to update based on your recent posting activity.

(NOTE: you can only hold one forum badge at a time)

Dig Your Own Grave:

The Yack Badge - awarded for leaving 100 or more comments on Dig Your Own Grave posts.
Gold Medal - awarded while you hold 1st place in a Dig Your Own Grave highscores game.
Silver Medal - awarded while you hold 2nd place in a Dig Your Own Grave highscores game.
Bronze Medal - awarded while you hold 3rd place in a Dig Your Own Grave highscores game.
Multiplayer Gold Medal - awarded while you hold 1st place in a multiplayer game leaderboard.
Multiplayer Silver Medal - awarded while you hold 2nd place in a multiplayer game leaderboard.
Multiplayer Bronze Medal - awarded while you hold 3rd place in a multiplayer game leaderboard.

(NOTE: Multiplayer badges only apply to the Monthly Points and All Time Points and Skill Rankings leaderboards)

Video Fantastica:

The Yack Badge - awarded for leaving 100 or more comments on Video Fantastica! videos.
The Video Noodle Badge - awarded for voting on at least 5 videos in the past 10 days.