Forum Moderators: travelin cat
When you speak to the new client, you'll want to figure out which breed of Mac user you're dealing with. If you're lucky, they'll be the Unix kind, that use open source Unix tools like the ones already mentioned, which you're probably familiar with.
If they're "the other kind" of Mac users, they may have a FileMaker Pro database set up, in which case you may have got your work cut out for you learning FileMaker and Lasso. (Or else help them out by talking them into SQL.)