Lots of threads with people having problems, so I thought it would be nice to know what's WORKED for you.

Here are a couple little ones from me that made me go "cool"

Avatar image off my Flickr account.

-Log onto Flickr from the browser
-select image, and download to image directory
-crop in image editor (nice that you can select image ratio)
-save image
-open contacts, select contact, select avatar image. Done


Bluetooth video from Symbian Phone

My son had a video shot on his E63 he wanted to send me
-Pair devices
-Selected video from E63
-Select send via bluetooth, locates N900, send
-N900 says accept? yes. Knows its a video and saves to videos directory, asks if you want to play once saves. yep
looks nice on the N900 big screen

Automatic clock adjustment and time shifting of my calendar upon arriving in a new time zone.

Mount N900 on Macbook via USB

Just plugged N900 into my Macbook pro. It says Mass storage mode or PC suite. I select mass storage mode. Mac book mounts the N900 with very nice little icon on the desktop. Where does it get the icon from?

The built-in icon that is on the file system!

Keyboard shortcuts... really nice I use all the time feature:
ctrl C for copy, ctrl V for paste, ctrl right arrow jump till end and left for jump to margin... ctrl+shift+ one of the arrows jumps one word and selects, shift+ctrl+p for screenshot... etc.

easily choose and copy a text a friend wrote and paste it in to your own text.

the merge contacts... really easy to merge and select common name.

Calender is really growing on me with all the possibilities of making multiple calendars in different colors... I have NEVER been this organized

Multitasking goodness in general... so easy to jump from one thing to another... looking something up on the net while chatting with a buddy and listening to some music.

UR-QUAN MASTERS!!! need I say more :-D

oh and all the little things you take for granted:
f.ex. led flashing when message recieved, missed call etc.
search contacts just by starting to type name on keyboard.
Multiple desktops. (with different or loopable wallpaper)
integrated Skype.

last but not least: the endless possibilities of open source.