Productivity
Google Pack is a great way to install several of the desirable enhancements to Windows in one easy process. Some of the programs included are Google Earth, Firefox, Adobe Reader, Picassa, Google Toolbar, Skype and Spyware Doctor. I highly recommend omitting Norton Security Scan. All of the other programs available through this site are safe enough, just some are more useful than others.
Open Office is a complete office suite for PC or Linux operating systems. NeoOffice is for the Mac OS. Both are free and compatible with Microsoft Office. You can create Word, Excel, Access and Powerpoint files and a share them with Microsoft Office users.