Freeware - Software

P2P
µTorrent - torrent client
Azureus - torrent client
BitComet - torrent client
ABC - torrent client
BitTornado - torrent client
eMule - p2p client
SoulSeek - p2p client
Shareaza - p2p client
DC++ - Direct Connect network client
PeerGuardian - IP blocker

Chat
Miranda - chat client
MSN Messenger - chat client
Yahoo Messenger - chat client
QIP - chat client
Gaim - chat client
JAJC - chat client
HydraIRC - IRC client
Talkative IRC - IRC client
IceChat - IRC client
Skype - VOIP client
Google Talk - VOIP client
VoipStunt - VOIP client
Gizmo - VOIP client
Wengo - VOIP client

Security
AVG Free - antivirus
Avast Home Free - antivirus
AntiVir PersonalEdition - antivirus
BitDefender Free - antivirus
ClamWin - antivirus
CyberDifender - Internet Security Suite
Ad-aware - anti-spyware
Spybot: Search & Destroy - anti-spyware
Windows Defender - anti-spyware
SpywareBlaster - anti-spyware
Spyware Terminator - anti-spyware
Tootkit Reveaker - rootkit detection utility
Winpooch - system protection
HiJack Free - system protection
HighJackThis - hijackers detector and remover
Kerio Personal Firewall - firewall
Sygate Personal Firewall - firewall
ZoneAlarm - firewall
AxCrypt - file encryption
Simple File Shredder - securely delete files
PuTTy - SSH client
KeePass - password manager
LockNote - password manager
nPassword - password manager
Microsoft Baseline Security Analyzer - identify security misconfigurations