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
16 awarded
Question favorited by 25 users
Question score of 25 or more
86 awarded
Asked a question with 2,500 views
553 awarded

Answer Badges

First to answer and accepted with score of 10 or more
448 awarded
Provided non-wiki answers of 15 total score in 20 of top 40 tags
Accepted answer and score of 40 or more
13 awarded
Answer score of 25 or more
97 awarded
Answered a question more than 60 days later with score of 5 or more
157 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
184 awarded
Left 10 comments with score of 5 or more
21 awarded
Visited the site each day for 30 consecutive days. (Days are counted in UTC.)
134 awarded
Earned 200 daily reputation 50 times
Actively participated in the private beta
68 awarded
10 posts with score of 2 on meta
40 awarded
Posted 10 messages in chat that were starred by 10 different users
22 awarded
Active member for a year, earning at least 200 reputation
743 awarded

Tag Badges

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

Moderation Badges

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

Other Badges

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