Jono Bacon is a long time Linux activist from the United Kingdom and currently works for Canonical, the company behind Ubuntu. He is their community manager.
He has written a book about communities in the context of groups that share common goals like support for or development of open source software. The book has been recently published, and is currently on my to-be-read bookshelf (one sadly sagging from the weight of volumes there). However, Mr. Bacon has taken the extra step of getting his publisher to agree to an unusual thing. The book is also available for free.
Even if you are not a part of the writing or support of open source software, you may be reading this blog because you are part of the education community. You may also be part of the group MassCUE, for which this blog represents a special interest group. MassCUE is Massachusetts Computer Using Educators with a strong community.
Since you don’t have to pay for the book, you can certainly afford to read it. Go to it!