1. Virtualbox
The best virtual machine enabler host, now bought by Oracle Corp.
2. Open Suse 12
Easily the best operating system ever, virus free, open source and very comprehensive and easy to use.
3. Oracle XE
Easily one of the best database systems ever,rock solid, virus free and comprehensive.Ofcourse there are others Postgres SQL, MongoDB etc.
4. Axcrypt
Easily the best encryption system ever, for Windows, very easy to use, helping compliance with HIPAA and is open source
5.VPNs Linux VPN servers-ipsec/poptop/sslvpn for Windows & Linux clients, very easy to use, open source and secure