Useful links

Security

Microsoft Technet Security centre

Apple Security updates

Windows 8 security enhancments

Windows 7 Security Features

Mac OS X Security Architecture

Windows Vista Security Guide

Vista SP1 Security improvements

Criticism of Windows Vista UAC

Microsoft on XP SP2

What is XP SP3?

BitDefender Real-time Virus Report

Viruslist.com by Kaspersky Lab

Symantec Internet Threat meter

Secunia - Vulnerability & virus info

Zero day Initiative

Troubleshooting

DLL Downloads

Cisco-Internetwork Troubleshooting Handbook

OS X Maintenance & Troubleshooting

Free Apps

Sourceforge

Warning!- Sourceforge has started bundling crapware with their installers & in most cases without the developers' knowledge. Always go for custom installation when downloading apps from them & opt out of junk or just avoid them completely.

Snapfiles

Nonags