I have slowly but surely been moving my life from the PC to the Mac. Here is a list of useful things:
Moom - a very cool tool for moving and zooming windows
Mint - from Quicken - a wonderful replacement for Microsoft Money. It is cloud-based, but makes budgeting and tracking as a family very easy.
Alfred - I use it to launch programs, search for files, search evernote, create reminders - all from one central place. It seems like every action I initiate these days goes through Alfred with its extensions.