OpenStreetMaps certainly has this facility, but the barrier to entry is too high unless you're interested in mapmaking. Also you need to consider social issues. The OSMappers would no doubt be very happy for you to add POIs for public toilets, but would probably consider that POIs for (say) rumored UFO abduction sites was not within the spirit of the OSM project.

What I have in mind is that anyone could edit a web page or wiki page. Perhaps the convention could be as simple as "Put the points of interest in a bulleted list. For each one, list the name followed by the GPS co-ordinates, followed by optional IMG tags and a textual description. Voila, your POIs are immediately accessible to anyone with a Maemo device.

Regards,
Roger