I have made an initial unofficial build of ScummVM for the N900. It seems to work OK.

It requires some additional packages, all of which are available in the extras, extras-devel or extras-testing repositories, such as: libsdl, libmad, libvorbisidec, libflac, libasound. 

All I really did was:

• Apply the supplied patch for the N810 (Maemo 4) devices and added the -lX11 flag to linking, since otherwise it could not find the symbol XStoreName which comes from libX11.
• Add RX-51 (=N900) into the list of keyboard-equipped Maemo devices in the part where it figures whether or not it’s running on a keyboard-equipped device or not
• Fix the window focus – due to a Fremantle SDL bug (https://bugs.maemo.org/show_bug.cgi?id=5153)
  you couldn’t use the keyboard at all since all keypresses went to
  wherever you launched Scummvm from (homescreen -> calls up the
  Contacts page, xterm -> keypresses appear on command line) otherwise.

I would like to stress out that this is completely based on the previous Maemo porting work and all I did was the abovementioned things on top of that.

Now that I have this running, things to do would be (in no particular order):

• Figure out which parts of the Maemo 4 patch are still a) necessary b) working anymore. At least the part that adds the application into the launch menu is still working. The part about bypassing GCC 3.x bugs may not be.
• Come up with new keypresses for the essential features like saving and loading games
• change the default directory to /home/user/MyDocs (or something) when adding new games
• Upload the binary package to maemo.org Downloads and fremantle repositories
• Submit things to the mainstream project in case I actually do any production-quality code changes, instead of random hacking around (though I’m not hiding anything, all my stuff is available upon request if someone really wants.)
• Try to get the screen centered
• Display the mouse cursor (actually already seems to happen in AGI games like Larry 1)
• Enable fullscreen mode with some key combo

Things I don’t think I’ll be able to solve:

• Music playback is sometimes choppy
• The file selector dialog is not very usable on a touchscreen device

Screenshots and video!

Youtube video:

Screenshots on flickr: http://www.flickr.com/photos/32856926@N06/sets/72157622620009580/

Oh and btw, first post on my all-new personal blog! Forgive me the boring default look and feel as I continue to tune it to my tastes..