I wouldn't clap when my plane lands (unless the Pilots does an incredible Job like landing after this http://www.youtube.com/watch?v=nNR0a4TMxeA )

Actually the only time I can remember people clapping was last Month on FR to BGY. Not sure if it was because there were so many "first time fliers" on board, or if it really is typically Italian, as seen in this funny "Europe and Italy" Flash.. :-)
http://www.infonegocio.com/xeron/bruno/italy.html

But generally I find it embarassing. You wouldn't applaud to a busdriver bringing you safely to the station...