Fossil makes it really easy to clone repos. It would be great if one could make "drive-by" contributions to an open source project by passing back fixes made in a cloned repos back to the developers without requesting write access for the repository. 

Bazaar has a cool feature called "Merge directive" that packages all changes relative to the partent branch:
http://doc.bazaar.canonical.com/bzr.2.2/en/user-guide/sending_changes.html

It would be cool if Fossil supported this feature as well