I just finished a little tool that converts the plural rules from the CLDR format to the gettext format.
IMHO it's good enough to be used as a common reference, since:
1. It's generated automatically: no human errors ;)
2. When Unicode publish a new CLDR release, it's very easy to keep that tool updated (it's as fast as copying 3 files)
3. The tool implements extensive tests to check its algorithms (all the cases are tested against the examples that comes with the CLDR data itself).
You can find this tool here:
And its html result can be found here:
--
Michele