I just thought of doing a theming thread but it fits in here as well!
the stuff is not only desktop but well will repost it somewhere else if needed

as the n900 is capable of GL and the fancy blue spirit desktop theme already shows of a some alike 3D movement of the desktop elements, I thought of a desktop with a globe as background (moon, earth, osmarender, you name it) rotating as you move your desktop-view, also capable of centering your current location to the home (first) desktop. (I was thinking of compiz's desktop cube as globe)

to the frontends people may like (or not, I dont care)

powermanagement, events:

• some kind of laptop-mode-tools with easy to use shifters and buttons input
• event handler frontend to manipulate "keyboard-in/out", "powerbtn" registration used to trigger something

WiFi:

• show (and choose for connection) nearby WiFi devices with signalstrength as indicator for distance (cant remember the name but something like this is build in with the latest DD-WRT firmware)
• a kismet-like and alike toolset

file-handling, -system:

• macroscripting (automagicaly records what you do and provides a button to do it at once, again and again)
• fileconverter (ps2pdf jpg2png etc) frontend
• lvm (should be capable of moving files to another device to remove the SD card)
• crypting. remember its eating CPUs so settings with low CPU usage or single-file-encryption should be enough, this tool should also automagicaly lock the vault after time and ask for passwords if needed
• GnuPG may be useful as well
• networkmount. mounting your windows/linux/network storage (maybe in relation to your WiFi network?).

images:

• watermarker, a tool to make a pics background convert to alpha transparent and add it to a folder/filelist of pics at X,Y position and add this text at X,Y xPts huge
• gif-o-mator. take this $list of pics and create a 15sec $gif

I cant give desktopPC examples as I'm not familiar with GUI tools for background issues (I'm more of a vi guy). I am a dedicated debian fan and will have my first smartphone with the n900 (but was already sucking all the good out of my SE-W880i with javaprograms)