What should you do with your Mercurial patches for Sage? You should post them on the Sage trac server.
The Sage trac server, located at http://trac.sagemath.org/sage_trac/, is where Sage bugs are listed and patched, new code is posted and reviewed, and ideas for extending and improving Sage are discussed. Thus if you find a bug in Sage, or if you have new code to submit, or if you have corrections for the documentation, you should post on the trac server.
Items on the server are called ``tickets'', and anyone may browse the tickets: just visit http://trac.sagemath.org/sage_trac/report. You need to open an account, though, if you want to comment on a ticket, submit a patch, or create a new ticket. See the web page http://wiki.sagemath.org/TracGuidelines for more information about obtaining an account, as well as general guidelines for using the trac server.