I have given up trying to keep up with all the software that changes on an almost daily basis.

Here are links to major sites that track virtually every software release & update that happens.

Software Downloads, Updates, Shareware & Freeware
Download.com
Info-Mac
MSN
Shareware.com
Tucows
Version Tracker
ZDNet

Major Software Houses
Adobe
Apple
Microsoft

Also have a look here at my computer links page