I know I can display a relation/way/node on the map with a url like "www.openstreetmap.org/?relation=######### " but is it possible to display more then one item at once? Like relationnumber xxxx and yyyyy in one view?
Have a look at the webservices http://www.openstreetbrowser.org and http://ags.misterboo.de or http://osm.misterboo.de/education/
There are more than one special objects displayed. If this comes near your aims, contact the authors.