Bonk!

List gaining length. Feel free to suggest more.

Compression:
KGB Archiver
Universal Extractor


File Tools:
File Cutter
Gmail Drive


File Recovery:
Recuva


Antivirus:
AVG free
Avast
Avira


Cleaning:
Ccleaner
Tune up


Firewalls:
Comodo
PC Tools Firewall Plus
Zonealarm


Encryption:
Truecrypt
Twofish
Toucan

Steganography:
-None-:[