For those projects that are still using the OSGeo trac,
I've just enabled inter-trac links.
This means you can reference tickets/wikipages/changesets of
any OSGeo project using trac from any other trac instance by
simply prepending the project name in the link, like:
geos:changeset:2234
osgeo:#45
ubuntugis:wiki:WikiStart
The project name is the last portion of the trac entrypoint:
PostGIS <--- "postgis"
I hope you'll find it useful. Next step will be figuring out a
way to automatically show the incoming link from the target 
--strk;