Those are called POIs (points of interest) in the maemo mapper world. Just tap and hold anyplace on the map. When the menu comes up select "Tap Point > Add POI..."

You can also import them from a GPX file that your GPS receiver might make. I'm working on a simple converter script to import the google maps "My Places" points into Maemo Mapper. It's a little rough/complicated right now, but it's over here:
http://www.internettablettalk.com/fo...ad.php?t=11323

There's also lots more info in the Help file and on gnuite's site.

-John