You haven't mentioned whether you need a portable or (larger) desktop size, but all Lacie's on
this page (desktop) or
this page (portable) are both firewire and Mac compatible.
I typically "roll my own" FW drives (buying external cases and drives separately), but most, I believe, have had good experiences with Lacie on these boards.
Perform a search on "Lacie" in the search box.
Good luck, and welcome to Mac.