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

Asked a well-received question on 30 separate days, and maintained a positive question record
51 awarded
Question favorited by 25 users
Question score of 25 or more
34 awarded
Asked a question with 2,500 views
84 awarded

Answer Badges

First to answer and accepted with score of 10 or more
475 awarded
Edited and answered 50 questions (both actions within 12 hours, answer score > 0)
2 awarded
Provided non-wiki answers of 15 total score in 20 of top 40 tags
Accepted answer and score of 40 or more
2 awarded
Answer score of 25 or more
34 awarded
Answered a question more than 60 days later with score of 5 or more
584 awarded
Zero score accepted answers: more than 5 and 20% of total

Participation Badges

Voted for a candidate in the final phase of an election
66 awarded
Left 10 comments with score of 5 or more
25 awarded
Visited the site each day for 30 consecutive days. (Days are counted in UTC.)
67 awarded
Earned 200 daily reputation 50 times
1 awarded
Actively participated in the private beta
10 posts with score of 2 on meta
28 awarded
Posted 10 messages in chat that were starred by 10 different users
17 awarded
Active member for a year, earning at least 200 reputation
721 awarded

Tag Badges

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

Moderation Badges

Raised 80 helpful flags
9 awarded
Voted 300 or more times
77 awarded
Completed at least 250 review tasks. This badge is awarded once per review type
7 awarded
Edited 80 posts
23 awarded
Edited 100 posts that were inactive for 6 months
4 awarded
Up voted 100 answers on questions where an answer of yours has a positive score
17 awarded
Edited 50 tag wikis
4 awarded
Created a tag used by 50 questions
40 awarded

Other Badges

Shared a link to a question that was visited by 300 unique IP addresses