I'm migrating an old MySQL based app to Postgres at the moment. Heres some of the things I'm looking at in addition to the base tools.

1) taps ( done by some people from Heroku ) : https://github.com/ricardochimal/taps and http://adam.heroku.com/past/2009/2/11/taps_for_easy_database...

2) mysql2psql : https://github.com/maxlapshin/mysql2postgres

3) Just slurping in the data via the FDW feature for 9.1 , http://www.pgxn.org/dist/mysql_fdw/1.0.0/