For video chat, see here:
http://www.internettablettalk.com/fo...8313#post98313

To use it as a still-shot camera, Knips works under OS2008 on N800. It will probably work on the N810 too.
http://www.anderenen.de/anderenende/maemo.html

There's also a command-line program called Motion kicking around somewhere that worked under OS2007. Haven't tried it under 2008 yet.

Actually, I see two Motion apps...
https://garage.maemo.org/projects/motion/
and
http://www.internettablettalk.com/fo...ead.php?t=4869

I used the second one (docs here), but the first one looks easier.

BTW, the camera on the N800 is not very good quality so don't expect much... not sure about the N810.