In a surprisingly well-kept secret, HgWeb and HgWebDir support RSS. Details below.
mercurial is a neat distributed revision control tool which has a web interface called HgWeb. Anyway although there are no links on the web page generated by HgWeb nor any obvious documentation with regards to RSS, you can get it.
Even on a per-file basis! So, for an rss-feed for a repository:
For an rss feed for a particular file: