We have neigbours who moved in next door last year. Now deep in to the summer and this guy treats his garden like a bin. Full of black bags, broken beds, toys, the lot. He has a pile of toys outside in his back garden and his kids go and fetch them out to play with them, climbing over other toys to get to them.
My only response has been to garden like mad and keep my side looking tidy in the hopes it'll shame him in to cutting his grass at least.