I thought I should share my current favourite Ubuntu patch.
While hunting for easy RC bug fixes yesterday, I stumbled across mit-scheme_7.7.90+20090107-1ubuntu1.patch [roughly 9MB]. It contains a Debian .deb to bootstrap the Ubuntu mit-scheme package (bug filed). Nice.
Now, to be fair, Debian has a bootstrapping problem for mit-scheme as well - it requires itself to build, but is currently uninstallable in unstable (although zack's on the case). Having looked at the problem, I think the best thing to do in the long term would be to package mit-scheme-c (which appears to be a superset of the upstream tarball for mit-scheme?) and then use that to build the other package. This would also provide a version of mit-scheme for arches other than i386. If maintainer-built binary packages are going to get thrown away at upload time, that would have been the only way to solve the bug, I think.
(I don't mean to fuel the Debian vs. Ubuntu flames; it would have been nice if the MOTUs could have fixed this in less of a hacky, license-violating way, but they did at least get the package to build, which is more than Debian can do at the moment. I intend to keep a closer eye on Ubuntu bugs and patches for the various packages I work on, because keeping divergence to a minimum should benefit both distributions.)