One way to do it is to open the file on a Win machine with Access installed, then export the tables to 'CSV' or 'SQL dump' files. Take those exported files and import them into your DB (MySQL is a good choice).
As far as a 'helper app' to convert them, there isn't one that I'm aware of that'll run under OS X. The last time I searched for one was a year ago or so, but nothing came up then and I seriously doubt there was a strong demand for such a thing. Access is a bit weird in how it does things, which would probably be a nightmare to have to convert.