Tex-Edit Plus - This is a small, fast text editor that is fully AppleScriptable and AppleScript Recordable. $15 Shareware.

IP Net Router - Good for sharing an Internet Connection between multiple computers. Shareware. Not needed in Mac OS X 10.2 and later.

Graphic Converter - Opens just about every image file type there is. Bundled with Apple computers that ship with Mac OS X. Shareware.

Aladdin Stuffit Expander - Opens just about every compression/encoding format that there is. Formerly bundled with Mac OS X. Freeware.

PrintToPDF - Makes PDF files for 1/10th the price of Adobe Acrobat. Can be read with Acrobat Reader. Not Needed in Mac OS X.

Acrobat Reader - For reading PDF files. Available for just about every operating system that's shipping, and bundled with Mac OS X. Freeware.

Disk Warrior - If Disk First Aid can't fix it, odds are that Disk Warrior can. Recommended over Symantec's Norton Utilities / Norton Disk Doctor.

TypeItForMe X - This is a text macro tool much like Microsoft Word's AutoCorrect feature. You define a number of abbreviations and the full text entries that they represent, then you watch the Mac expand them on the fly even as you continue typing. This version is for Mac OS X 10.1 or higher. However it uses your classic abbreviations file seamlessly.