I came. I saw. It was empty so I edited the wiki HOWTO: about
using bluetooth to connect linux.

Since my laptop has lost her wifi, connecting to the N800 and using
the N800 as a modem is very important to me. I am on an extended
trip and have Internet access to wifi but not ethernet. I have a
lot of work to do in a short time and having my laptop cut off
from the Internet is a big problem. The N800 connects easily to
the Internet but without my usual big screen, hard disk, and many
other advantages of the laptop over the N800; twelve hours a day
on the N800 is only a small fraction as productive of 12 hours
a day on the laptop. The N800 modem is an excellent solution for
connecting a laptop with weak or non-existent wifi to the Internet.
So how do I use it as such?

I have the same question but connecting the devices using usb rather bluetooth. Is it possible to set up networking over usb where the n800 is the gateway.

Hmm...should be possible.
Look here for a good explanation of what you're tying to do only substitute the BT network interface for the hardwire LAN interface on that page.
Basically what you want to do is to bridge the wi-fi connection with the BT connection, linking the two. Both will be on separate subnets of course, but the BT subnet will be routing it's traffic through the wi-fi subnet to get out to the internet.
I'm really no good at teaching or explaining anything.
Good luck!

Dear peterjb31 Thanks for being the 1st to speak up that you want the same
thing but perfer usb to bluetooth. I feel the same way but think this may not
be possible because the N800 usb cannot act as a host. It is crippled to
client only.

Dear iball,
Thanks for the good reference. It will help but I for one am not there yet.
I hope others can carry forward the link you gave with more specifics for
the N800.

It doesn't need to be host, it can function on the usb cable as a client but be a host over networking.

peterjb31 enlightment, "
It doesn't need to be host, it can function on the usb cable as a client but be a host over networking " is good to know. Then the link given by iball
http://www.sorgonet.com/network/adva...lesswithlinux/
just needs to be changed a little.

I have a major presentation at PyconUK and then a catch up on many
things after a Summer away before I can consider lifting a hand on
this. Besides, this forum probably has many better hands. If someone
changes the variables in the sorgonet.com advancedWirelessWithLinux
or comes up with a better solution, please post it here.

Am I missing something? If your laptop's built-in WiFi died, why don't you just plug in a WiFi USB adapter? Or better, of course, replace the built-in WiFi card.

I second the previous poster. You should be able to get a wi-fi USB stick from almost any gadget/electronics shop (unless you're out in the bush of course, which is where I sometimes find myself). With your linux laptop you should be able to get almost anything working, just use the windows driver together with ndiswrapper (search for it on sourceforge and get the latest version from there, the distro versions tend to be old).
Or get a cheap travel router, e.g. asus 330g. Powered by usb, plugs into ethernet port. No drivers needed. Very useful also for the N800, as you can turn a switch and use it the other way around: Plug it into an ethernet outlet and you have an access point for your N800. Good for e.g. hotels with ethernet but no wi-fi.

As for using the N800 as a wi-fi interface for a laptop, that should also be possible - but not so easy as the above!
I did set up my linux laptop as a network interface for my BT Palm, with BT DUN. In principle the procedure would be to set up an N800 exactly the way I set up my linux laptop, and then figure out how to set up the linux laptop to connect over BT DUN. Haven't done that part yet so I don't know how much work it would be.

EDIT: There's actually one more reason for wishing to use the N800 as wi-fi interface for the laptop.. the N800 is just so unbelievably more sensitive than any USB stick, or in fact any other wi-fi interface I've tried so far. With my N800 I can sit in the middle of a park and connect to any of the cafeteria wi-fi APs surrounding the park, with my laptop I must in practice be inside. Can't even have my cappuccino at the outside tables. Heck, after some reconfig in the office I can't use wi-fi with my laptop anymore, only the N800 works. Too weak signal for the laptop.

Actually, there are many more reasons for wanting to use the N800 as a super
sensitive external modem instead of a usb stick. I'm amazed that so many
Linux gurus want to argue every use case instead of being focused upon
technical progress for every possible use cases. Sorry, I do not have time to
get involved in the usual Linux wars. If someone wants to help that is great.
If someone wants to argue that all users should follow only one path, I am
already bored with that type of reasoning on the forums of all platforms.