i made some reports about administrative boundaries in OSM. You will also get a hierachical boundary-structure (parent/child) for each country.
As a little plus there is also the possiblity to generate shape files for each country.
A pre-generated report with data from 08 May 2012 can be downloaded here
Shapefiles (860MB) are seperate download here (Put the shapes folder in the website folder to get the links working)
Source code is on github
Any feedback is welcome.