Same as Hordeman :
Open Office works fine, thanks to Qole's amazing work !
I find it very usefull.

I really love using FBReader too ... because the device is really pocketable at have a very good screen for indoor AND outdor use.
I find reading on the n810 better than on real paper !

Music listening at work, without headphones is very good too, thanks to the built-in speakers and the very good player : Canola.