I saw this hilarious truck parked in front of Walter Johnson high school today (Rockledge Drive in Bethesda):
This particular one is owned by the same company that owns Party Warehouse, etc.
They offer 35 flavors of shaved ice, and will drive right up to your party to complement your Moon Bounce.
Snowie is a Utah company that will sell you a brand new bus for $78,900, with numerous variations.