Gentoo MacOS. More on what it is here.
I guess the plan is therefore:
1 - Get to grips with Fink on the Mac. (I am already happy with the basics of apt-get from using Debian GNU/Linux).
2 - Install Gentoo on a PC and get the hang of that, especially portage.
3 - Install the Apple Developer Tools on the Mac (they're on the second OS X install CD, I believe).
4 - Give Gentoo MacOS a try.

Just to demonstrate what a newbie I still am, I only just found the command to tell me the size of a directory. It is simply du, (display usage). The command also responds to the old -h switch, for human-readable values (-m or -k also work, just as for df, which I have been aware of for some time).
du lists the size of all directories and subdirectories under the current directory, and handily finishes it's listing with the total size of the current directory .
So, to find the size of a directory, cd into it and type du -h (best not done in / on a slow machine!). The last line spat out will be the current directory size.

Software Express for Solaris - Solaris free for non-commercial use.

Mad Penguin - source of the article below. Looks pretty useful.

Mad Penguin :: Howtos : FreeBSD Install Guide

Linux.com | How Linux boots

linux pc's from uklinux.net (not even up yet!).

I am still a Linux newbie. I mean, I play with Linux when I can, and I run a server at home that does file server (Samba), web server (Apache) and DNS (BIND) duties for my home LAN. Trouble is, it never goes wrong so I only really play with Linux when I have the time and want to learn how to do something new. Anyway, today I wanted to accomplish two things:
1 - Get a samba share to create all new files with a certain group ownership and group permissions, so that me or the Mrs can change files that the other has put there
2 - Learn how to see if anyone is connected to the Samba server.
As always, when you've figured it out, it's a piece of piss,
1 - Use one or all of the following in the appropriate share stanza in smb.conf:
force user
force group
create mask
directory mask
2 - One word (command): smbstatus
:)

Syllable - another Open Source O/S!

SkyOS -- Your PEACE-FULL future Operating System.
There is just too much cool-looking stuff out there to play with. I know nothing about SkyOS, but it looks nice.

LyX - The Document Processor.

Debian Planet - News for Debian. Stuff that *really* matters. :)

haiku - open source BeOS. Definitely gonna have a play with this.

OK, so I have mod_dav running on my Debian 3.0 server. Apache is at version 1.3.26, which is up to date in Debian-world.
I can connect with cadaver, the command-line utility on Linux, with no problem.
Windows XP, however, is being a right pain in the arse - authentication is failing. What a surprise.
Here are some links:
One from CalTech on
How to setup a Windows XP compatible WebDAV folder under Apache.
One from a LUG mailing list in Boulder with some weird stuff about syntax for authentication from the XP end.
One from some pipermail list on a "Solution for basic authentication with Windows XP and mod_dav" - looks much like the CalTech one.
Also, some relevant stuff on google groups here .

mod_dav Installation and Configuration - I'm having some problems.