See the mainstream
software page for the most widely used downloaded software such as RealPlayer or Adobe reader. This page covers more specialised or niche tools, or items which extend mainstream functionality to the freeware/shareware user.
If you have a Windows XP system, Google Pack includes several Google tools and commonly used software products, and will keep them up to date (28 Jan 2006)
This page has been checked through, and quite extensively pruned. Google is very good at finding things – add free download or shareware to your search. I'm not a regular Linux user so the Linux stuff is only discovered by seredipity.
Availability key: Mac ⊕ (!! for Classic only) Windows ⊗ (!! for DOS) Linux ◎