Yes, included with OS2008, and probably with older Tablet OSes, is backup software that will allow you to backup selectable components (documents, apps, etc) and back them up to a desired location such as a memory card.

Alternately, with a little effort, you can set your tablet to boot off the memory card, thus you can backup the card on your computer, etc. The N800 is ideal for this as it has two full size SDHC card slots, you can use either one for the OS, and the other for expansion.

I dont personally have any experience with the OS from card booting but forum posts indicate its relatively painless.

Why I bought four (for myself and relatives):

Two full size SDHC slots, 802.11a/g, bluetooth, touch screen, pop out rotating vga webcam, removable battery, usb (with host mode or seen as two removable drives).. web browser with flash 9, mp3, divx (without conversion), upnp, rdp, telnet/ssh.. and all for often under $250 (I actually paid $215 after taxes each - Christmas sale price).