BitPim is an open source, cross-platform application (including, obviously, an OS X version), written in Python. BitPim allows you to manage phonebook, wallpaper, ringtones, and calendars on LG phones (and others). It supports importing vCard files, too -- so you can export from Address Book and onto your phone.
I'm using it with my new LG VX 4600 phone from Verizon, which although not officially supported by BitPim just yet, works when I tell BitPim I'm using a VX 4500.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050111122330634