Here I'd like to highlight the most important benefits for me:
- Networking - ability to make social connections with developers from other companies
- Learning - it's the right place to learn something for free and improve you skills.
- Knowledge sharing - you shouldn't always take also you can give something to others. In our case it's your knowledge. Most people are very kind and really like to share own experience.
- Public Visibility - here you can promote yourself as passionate and well skilled developer
- Job Opportunities - you can find new contact which suggest a new job
- Find Expert - it's the right place to find the right people which might help you to solve some technical problems
- Become an Expert - it can happen
- Meet Nice People - just fact :)
If you have other nice benefits please add in comments.