In terms of apps, there are hardly any I'm afraid.It's really sad.
All I can show off these days is some of N900's OS capabilities.

Such as:
- MicroB playing youtube videos in the background while multitasking.
- mplayer playing videos in the background while multitasking.
- xterminal (lol)
- old school midnight commander
- Ability to use queen beecon widget to make nearly any widget.
- Integration of many online accounts in contacts/conversations.
- Dual booting to NITDroid. But even HTC HD2 do this much better already.

There are far more cool stuff in Android/iPhone than N900 that's for sure.
But I still like the N900 due to hw keyboard, awesome multitasking capability.