If you want to connect to an ethernet with no other machines, you'll need USB host mode and some USB ethernet dongle; not sure if anyone has done this on the N900 yet.
If you have a networked host machine (with a free USB host port) that can route your traffic, you just need PC suite mode.
And if you don't need too much bandwidth, and want a little more convenience, you might consider a BT dongle for the networked host and PAN, but that's outside the strict scope of your query.
If you want to connect to an ethernet with no other machines, you'll need USB host mode and some USB ethernet dongle; not sure if anyone has done this on the N900 yet.
+1
i actually saw a youtube video in the h-e-n thread about somebody getting this to work.
I have an alfa wifi adapter and a powerful antenna and i get internet that way and the net i get is probly like 300 yards away which my N900 isnt going to pick that up so i guess from reading everything here the awnser is flat out NO you cant.
O.k. i guess i'll have to go to a cafe shop,micky D's or public library.
The response you got was mostly due to the way you asked, but you can find various solutions to do what you want by reading the wiki at wiki.maemo.org, or you could even just read the first reply properly.
The first reply even said he wasnt sure if it has been done before and im not about to subject my N900 to experiments since im not rich.
He said he wasn't sure if something very specific had been done or not. Depending on what exactly you wanted, it may or may not have been (though it's looking like the former) the same thing you were asking about.
I am pretty sure it's possible to just use a usb-to-ethernet adapted, and plug the other end into the N900. There's no easy way to do it, you'd need power kernel or mad developer to install the necessary usb module software on your N900, and you'd probably have to do some command-line stuff to make it happen. But it shouldn't be impossible.