I've been participating in a weekly Mario Maker race: basically, people submit levels specifically for this contest (unreleased to anybody else until it starts), and then everyone.. well, races them.
I say all that 'cause afterward the codes are open to anyone, and the levels are generally well-designed, although sometimes pretty difficult.
This week's levels were all ghost houses, on account of Halloween being last Saturday. If anyone wants to check 'em out, here's a pastebin with all the level codes! http://pastebin.com/DTiNN89i
..and here's another set from a previous week as well. If I can find an easy way to share the others, I'll post them here xD http://pastebin.com/ki2fSk54