Software updates:
Secunia Personal Software Inspector
Microsoft Windows Update
Microsoft Office Update
Virus Scanners:
Kaspersky scanner/cleaner
F-Secure Rootkit scanner/cleaner
McAfee Free scan
Symantec Security Check
Trend Micro HouseCall virus scan
Panda ActiveScan
Avast
Gibson Research Corporation
Speed tests:
Speakeasy
McAfee Speedometer
Charter Speedtest
DSLreports Speedtest
Spyware checks:
AdAware
SpyBot Search and Destroy
Microsoft AntiSpyware
Spyware Doctor