Opensource solutions

I was thinking of opensource solutions which will help us to reduce liscense cost.Just googled in and found out few major solutions

1.Database

MySQL
PostgreSQL
MaxDB
Firebird
Ingres

2.Operating Systems

Linux (Redhat,Fedora)
ubuntu
FreeBsd
openbsd

3.Personal Computing

Haiku

4.Virtualisation

Citrix xenserver
sun virtualbox

5. Webserver

Apache

6. Storage

Openfiler
FreeNAS

7. Development

PHP
JAVA