Recommended Mac Software Part 1: Must Haves

• Firefox - I have to list this -- the best browser because of its terrific plugin selection. Alternately, Camino is quite slick.
  
• SuperDuper! - a commercial backup tool that is my favorite Mac application and maybe one of my favorites of all time. Backs your computer up live (using a great tool called rsync). If you have an external hard drive of a similar size to your regular hard drive, you can back up your whole computer. If your hard drive ever crashes, you plug it in and hold option at system startup. Magic.
• Transmit - a strong commercial FTP/SFTP client but is rapidly being overtaken by the free Filezilla. Still Transmit ties into the automated system features extremely well.
  
• AppFresh - checks versions and makes sure you have the latest and greatest of everything. Not the best at actually *getting* those files (the download sequence is a little iffy) so some manual action is required. Non-free.
  
• AppZapper -- good for removing all traces of a program. Non-free.
• Cog - although not regularly updated, my favorite music player. Will work with your keyboard backward/pause/fast forward and volume controls as well as your remote control.
• Disk Inventory X - helps you track down space-hogging files
• EZ 7z - although Mac supports creating and opening ZIP files, there are much better tools out there, especially for collections of text documents or spreadsheets. 7Z is one such alternative. Your recipient will need a 7-zip decompression tool like Unarchiver.
• Floola - because iTunes blows.
  
• iPodDisk, which treats any iPod like a regular disk, which should come standard with every Mac.
• InsomniaX - allows you to close the lid of your computer without it going into standby.
• VMware - the best virtual machine player. Parallels is way behind and more annoying -- I haven't tested Sun's new, free VirtualBox.
• iSerial Reader - necessary serials for thousands of mac programs. Surprisingly complete.
• PeerGuardian - use to protect yourself if you use peer-to-peer tools like Transmit.
  
• TextWrangler - closest I've gotten to my beloved PSPad for PC. You might prefer xPad.
• The Unarchiver - opens a lot more compressed formats than the default tools.
  
• Xee - a more feature-rich graphics/photo viewer than the default viewer.