One of my favorite Trac features is the ease with which you can link from Tickets to Changesets and from Changesets to Tickets.

Text input of [256] is interpreted by Trac as a link to Changeset 256, while text input of #256 is interpreted as a link to Ticket 256 - one can’t ask for anything easier to remember.

My only wish would be that linking from Changesets to Tickets would also trigger a Ticket update about a related Changeset commit. I guess I’ll be forced to write that as a Subversion trigger unless I get lucky Googling for prior art.