I took the plunge into linux back in November and I've been loving the challenge but lately I've been thinking I need more of a challenge then I've been getting from Suse, Fedora, Ubuntu, RHEL, & CentOS they are all great distros but I'm looking to get more under the hood

I don't think I'm ready for anything like LFS but I would like more control of the system and how it's configured

so long story short (or at least not as long as it could be)
I'm asking for you opinions on what would be my next Distro
and I am always willing to RTFM

and just so you know here is my hardware

Dell Latitude D600
P-M 1.4 GHz
512MB RAM
ATI Radeon 9000
Broadcom 4700 ethernet
Dell Truemobile 1450 (Broadcom 4309 chipset)
40GB hard drive

I will be dual-booting this with the existing WinXP partition so I will only have about 10GB for the total install

I'd suggest Slackware or Gentoo. Or one of the BSDs.

Slackware or Gentoo

FreeBSD or Gentoo. Have a look at their homepages, they have great handbooks. What sets Gentoo apart from all other distributions is that you can specify exactly what you need through the use of flags; as they say, performance benefits more from trimming irrelevant dependencies than from setting inane compiler options. Then again, if you're impatient, compiling will be a major PITA. My first install of Gentoo with Gnome and KDE took me about a week...

You do not necessarily need another distro to get under the hood. Learn how to administer your distro using the command line only.
Only advantage of the above mentioned distros is that they force you to use the commandline as there are no nice looking GUI tools to add users, setup a firewall etc (at least not for Slackware).

thanks for your idea's
I'll just have to decide which of those to try

WIM,
what I basically want is a distro that can help me learn more about what goes on under the hood of a linux distro something that would help me to be more familiar with the command as well yes but when help is needed I would like to be able to ask for help and not be sent strait to a GUI if the distro itself relies more on the command line I'm going to assume so do it's users and therefor might be better suited to help in what I'm trying to learn
I would eventually like to understand enough that I can setup a server and not have to setup anything but SSH to administrate it
then someday (prolly like 20 years from now ) I'd like to build my own distro

You will not be sent straight to a GUI if you have a problem. Most replies here involve command line stuff and if you phrase your posts correctly, you will get command line answers.

But good luck in making a choice and enjoy the experience.

BTW the command line web browser is lynx

If you want to learn more about setting up servers etc, then you interests would be far better served by studying a book or an online tutorial than by switching distrubutions. Trust me, you can perfectly well set up Gentoo, Slackware of FreeBSD and still come away without any real knowledge of that sort of thing. Have a look at yolinux.com for "a few" pointers.