1. Office tools
    1. Microsoft Office 2008. To exchange files with PC.
    2. iWork '09. A better real office.
  2. Network tools
    1. Firefox.
    2. ecto. An excellent blog client
    3. FileZilla client
    4. Adium
    5. JollysFastVNC. A very good VNC client
    6. Remote Desktop Connection
  3. Graph/Image tools
    1. OmniGraffle Pro. A much better visio.
    2. Photoshop
    3. Aperture. If you take photos.
  4. Editors
    1. TextMate. Absolutely a must have
    2. TextWrangler.
  5. Development tools
    1. Xcode
    2. Intellij IDEA
    3. Eclipse
  6. OS enhancement
    1. Magnifique. Change skin for Leopard
    2. Monolingual. Remove unused languages and architectures files from disk.
    3. InsomniaX. Keep your mac running when lid closed
    4. Battery Health Monitor
    5. TinkerTool. Modify hidden system settings
    6. Paragon NTFS for Mac OS X. Better than MacFUSE solution.
    7. Fan Control. Speed up fan on temperature rising
    8. iStat menus. Best system monitor
  7. Other tools
    1. QuickSilver. Google Quick Search crashes just too often.
    2. cdto. Finder toolbar button to open a terminal window
    3. AppFresh. Keep all applications update-to-date
    4. iChm. A nice chm reader
    5. KeePassX. Keep password safely
    6. OmniDiskSweeper. Find what's weighting in your disk
    7. UnRarX
    8. VMware Fusion
    9. MPlayer OSX
    10. MacPorts. A gate to open source softwares. Seems better than fink to me.
    11. Counting sheep. A widget to sleep your mac at given time.