Here's the A7N8X family:
A7N8X "standard" has the dual-channel northbridge and the basic southbridge. It takes up to 400MHz FSB processors, doesn't have the Serial ATA controller or the fancy nVidia audio processors that the Deluxes have. Comes with a bracket for a gameport and additional USB 2.0 ports. No "speech reporter" feature. One network jack.
A7N8X-X is like the A7N8X "standard" but it doesn't have the dual-channel memory controller or the additional bracket for the gameport and USB 2.0 ports.
A7N8X Deluxe is like the A7N8X "standard" but it uses the fancy MCP-T southbridge, and as a result it has the nVidia audio processors and is now Soundstorm-certified. Also has an add-on SATA controller and SATA cables, and two 10/100MBit network jacks. Has the funky "POST Reporter" to tell you that "system now booting from operating system!" and stuff.
A7N8X-E Deluxe adds a 3Com gigabit-Ethernet controller in place of the second 10/100 network controller, and has a WinDVD suite, SATA power adapter cable, and it sounds like they threw some kind of WiFi-ready thing on there so you can buy an exorbiantly-priced Asus WiFi card if you can find it
A7N8X-VM is the microATX one with onboard video. Other than that, it's like the A7N8X "standard" except it's only rated for up to 333MHz FSB.
A7N8X-VM400 is a new version of A7N8X-VM that takes the 400MHz FSB processors.