There are hundreds of plugins available in the community plugin repository (http://community.elgg.org/). There is no way to review them all in this book, so we will highlight three of them. Each of these plugins is very popular within the Elgg community and is maintained by skilled developer(s). They are among the best demonstrations of what can be created with a plugin in Elgg.
Tidypics is a full-featured photo sharing tool that is actively developed.
Author: Cash Costello with contributions by several other developers.