The french OSM team has been playing with improved rendering in mapnik. Recently, they’ve introduced the idea of rendering sport tags for known sports by displaying the lines of the field. I like it a lot, it gives a much nicer display than having an icon of the sport :-)

You can see an example here, with tennis, football (soccer) and rugby fields: http://tile.openstreetmap.fr/?lon=2.44176&lat=48.83262&zoom=17&layers=B00000

They’ve also improved the rendering of golf: http://tile.openstreetmap.fr/?zoom=16&lat=48.72648&lon=2.60806&layers=B00000

I hope it’ll be picked up by other tile renderers :-)