OpenBSD – free, functional, secure 4.4BSD-based UNIX-like operating system. (I love pf).
FreeBSD – another free, functional, secure 4.4BSD-based UNIX-like operating system. (I love jails).
Slackware – the oldest Linux distribution, still alive. An easy and strong GNU/Linux, thanks Pat!
Slacky.eu – italian Slackware community. Howtos, forum and packages (in italiano).
BSD Mag – the BSD Magazine.
Slack Linux Fans – discussions About Slackware and Linux.
Stack Overflow – ask and it will be given to you.
TwoPenguins Productions – they’re great!
