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
47 awarded
Question favorited by 25 users
Question score of 25 or more
28 awarded
Asked a question with 2,500 views
62 awarded

Answer Badges

First to answer and accepted with score of 10 or more
415 awarded
Provided non-wiki answers of 15 total score in 20 of top 40 tags
Accepted answer and score of 40 or more
Answer score of 25 or more
25 awarded
Answered a question more than 60 days later with score of 5 or more
504 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
22 awarded
Visited the site each day for 30 consecutive days. (Days are counted in UTC.)
63 awarded
Earned 200 daily reputation 50 times
1 awarded
Actively participated in the private beta
10 posts with score of 2 on meta
26 awarded
Posted 10 messages in chat that were starred by 10 different users
15 awarded
Active member for a year, earning at least 200 reputation
655 awarded

Tag Badges

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

Moderation Badges

Raised 80 helpful flags
8 awarded
Voted 300 or more times
71 awarded
Completed at least 250 review tasks. This badge is awarded once per review type
5 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
16 awarded
Edited 50 tag wikis
3 awarded
Created a tag used by 50 questions
36 awarded

Other Badges

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