i have an n810, and i would like to triple boot it with maemo 4, android, and ubuntu desktop. i want maemo on the internal mmc, and the ubuntu and nitdroid on my 4gb sd card. is this possible? and if so, how would i select which one to boot? and, for the record, i am a linux n00b.

Last I checked, you can't multi-boot NITdroid.

You have to flash the kernel to switch between Android and OS200X.

Too bad nothing ever came of kexec...

However, the data files and such would stay intact. So you can have pseudo multi-boot.

And you can certainly have multiple copies of OS200X.

You want to look at PenguinBait's pbeasy. It makes it simple. You want the "console-tools" version as the previous versions are not compatible.
http://talk.maemo.org/showthread.php?t=25714

Oh one more thing by "ubuntu" you mean Mer, right? I'm just going to assume so as Ubuntu MID == Mer (they merged).

Also see:
http://wiki.maemo.org/Mer/Documentation/Bootmenu

is it posible to use the flash card(s) as external ram?????????????????????????????????????