This is sad.  I couldn't find one decent article online about motherboard stuff.  So, back home I come with questions.

Here is everything I plan to get (or swap over) for my planned system, which I was finally granted due to my birthday, although I was told I was going to get it in December of last year (I should've known better!).  (The forums aren't working at their best, so bear with me) And please, feel free to make suggestions.  I'm working with a decent budget, $600 or a little more.

-A sexy metal case and power supply - 300 watts
-[Motherboard unknown]
-Intel Pentium 4 Processor: 2.8 Ghz or up
-Corsair RAM (Circa 1Gb)
-Current Geforce Ti4200 64Mb Graphics Card (To be upgraded pehaps later on)
-Audigy 2 Soundcard
-Western Digital 250GB Hard Drive
-[Moniter unknown, need help with this]
-DVD-ROM
-CD-RW
-Iomega Zip Drive
-Wireless keyboard and mouse, sidewinder Force Feedback 2 and rudder/racing pedals later on
*Windows XP Home Edition
*Combat Flight Simulator 1/2/3
*Flight Simluator 2004: A Century of Flight
*Il-2: Forgotten Battles
*Command and Conquer: Generals Zero Hour
*Need for Speed: Hot Pursuit
*Medal of Honor: Allied Assault

This system is intended for gaming, music, gaming, movies and gaming.  What are ALL the things should I look out for in a motherboard (RAID, ATX, FSB... what is this nonsense?)

While I'm at it, depending on how complex it is, I think I'd like to set up my computer so that it'll connect to this one (the one I'm on now) via a LAN.  Is this easy to do?

ATX is the size of the board, and the connector locations. Most boards are ATX at the moment, just be carefull and get a full-size one

Get something with S-ATA for the harddisk if you are planning to get the WD 250GB drive, as that is a little faster

internal ZIP drive will kill performance on the IDE port it's attached on, so try to keep that one on a seperate one.

DVD and CD-RW should both be either ATA-100 or ATA-66

The thing is, I want to read 10 pages of info on all the details, I don't know about all these guys these tech review sites when they scoff at people with lower end systems, but $600-700 is a lot of money for me.  I'd read 5 hours worth of materials if I had to to make a good decision.

Crap, XP is shutting down, I'll finish this later.

ATA is a standard for harddisks and CD drivers
if there is a number behind the letters, it says something about the theoretical maximum speed.

In order of speed, starting with the fastest one
S-ATA, 2 different standards for this one. controller usually supports one of the two, harddisks adapt automatically.

ATA-133, the fastest one you can get on 80 wire flatcable. 133MB/s
ATA-100, 100MB/s
ATA-66, 66MB/s
ATA-33, same as UDMA, max speed 33MB/s

And the old ones:
PIO-4: ZIP-250 (2002 model) and possibly late model ZIP-100 drives
PIO-3
PIO-2
PIO-1