Parallels Desktop - Run Windows inside OS X
Transmit - Best FTP program out on OS X, so beautiful!
Unison - Usenet reader/downloader, made by the same people as Transmit. Very pretty interface.
Quicksilver - Catalogs EVERYTHING on your mac and provides an easy to use interface to open and manipulate any file/app. Takes a while to get used to but will end up being the one app you use most.
TextMate - Text editor built for web design and programming.
FontExplorer X - The best font management program I've ever used.
BitTyrant - Torrent app based on the popular Azureus client
FireFox - The best browser in the world, Need i say more?
Theres plenty more but these will do for now.