Probably the best way to find stuff on the board is to use the search page. Quite a bit of stuff is applicable across more than one appliance, so you might consider checking similar forums.
As for your specific questions:
The white IA-1s are the "US" versions, and lack ethernet ports and smart card readers. They run (natively) a version of WinCE designed to work with MSN. White IA-1's only have a 16Mb SanDisk (IDE flash memory)
The blue IA-1's (also called clippers) are essentially a white IA-1 with the addition of a smart card reader, AMD PCnet Home/HPNA network adapter, and (or course) a blue/grey chassis. They were sold in Europe, and use a version of BeOS (BeIA), and are capable of connecting to almost any network. Due to the larger size of the OS, clippers have a 32Mb onboard SanDisk.
They share everything else in common. Both styles have 32Mb of RAM (of which 2Mb is reserved for the graphics adapter), an AMD K6-x class CPU, 10" 800x600 DSTN LCD, Trident CyberBlade video controller, and, of course, a Compact Flash slot (complete with ejector button). The keyboard/mouse connect via infrared, and appear to the system as PS/2 devices.
What make these machines attractive is that they have integrated LCD's, small, svelte outlines, and, if you get a machine with an early revision of the BIOS, are incredibly easy to hack. The CF slot is essentially a second IDE controller - and indeed can be converted into such a port with an adapter.
Downsides include a, so far, impenetrable second version of the BIOS, crappy power supply (sometimes even failing to completely drive USB devices), and an infrared keyboard that lacks a few critical buttons- specifically F1 - F12, and DELETE.
Personally, I have four - all running FreeBSD and configured to come up as dedicated X terminals. I'm writing this post on one right now.
