Well, many of the bigger open source projects are collaborations between many people: Thus you do have a chance of finding a project written by good developers, and therefore improve your own coding style. Of course, it all depends if you actually memorise the stuff you read or not – But I guess you wouldn’t really read that much code if you didn’t.
In my opinion, you can learn the following from well-written projects:
- Coding conventions
- Solutions to common problems (Of course, this depends heavily on the “type” of the project)
- How to document code properly – If multiple people work on something, and the project is well-written, it probably also has a good documentation.
Of course, all of this is opinion-based, so you need to see for yourself.