Besides gaining reputation with your questions and answers, you receive badges for being especially helpful. Badges appear on your profile page, flair, and your posts.

Question Badges

Ask a good question on 30 separate days, and maintain a positive question record
31 awarded
Question favorited by 25 users
6 awarded
Question score of 25 or more
43 awarded
Question with 2,500 views
234 awarded

Answer Badges

First to answer and accepted with score of 10 or more
402 awarded
Edit and answer 50 questions (both actions within 12 hours, answer score > 0)
Provide non-wiki answers of 15 total score in 20 of top 40 tags
Accepted answer and score of 40 or more
6 awarded
Answer score of 25 or more
41 awarded
Answer a question more than 60 days later with score of 5 or more
66 awarded
Zero score accepted answers: more than 5 and 20% of total

Participation Badges

Vote for a candidate in the final phase of an election
Leave 10 comments with score of 5 or more
17 awarded
Visit the site each day for 30 consecutive days. (Days are counted in UTC.)
152 awarded
Earn 200 daily reputation 50 times
1 awarded
Voted 10 times, added 3 posts score > 0, and visited the site on 3 separate days during the private beta
38 awarded
10 posts with score of 2 on meta
26 awarded
Post 10 messages in chat starred by 10 different users
6 awarded
Active member for a year, earning at least 200 reputation
711 awarded

Tag Badges

You must have a total score of 400 in at least 80 non-community wiki answers to achieve this badge.
6 awarded

Moderation Badges

Raise 80 helpful flags
1 awarded
Vote 300 or more times
56 awarded
Complete at least 250 review tasks. This badge is awarded once per review type
8 awarded
Edit 80 posts
13 awarded
Edit 100 posts that were inactive for 6 months
Up vote 100 answers on questions where an answer of yours has a positive score
4 awarded
Edit 50 tag wikis
1 awarded
Create a tag used by 50 questions
28 awarded

Other Badges

Share a link to a question later visited by 300 unique IP addresses
1 awarded