I've seen the VFW (Veterans of Foreign Wars) sell paper or plastic poppies around Memorial Day. When I went to the UK last month they had a bunch of poppy-related memorabilia at a War Musuem I went to. It seems much more culturally prevalent in the UK than in the States.
In my Australian city (Adelaide) tomorrow at 1100 an RAF plane will drop 100,000 poppies over the city to commemorate the Servicemen of the 2 World Wars.
Our National War Memorial in Canberra has large bronze plaques with the names of all Australians who fell. The custom is to place a small paper poppy next to a relative's name. On one visit with my teenaged daughter I was attempting to do this, but the name was at the top of the plaque & beyond our combined reach. A visiting Japanese gentleman bowed & respectfully asked if he could do it for us.I was incredibly touched by this.