Pallets are great for jumps and are actually make for sick trail sections when used right, I've used them lots ion little drops and stuff too, great cuz most are either cedar or oak, so they're tough and dont rot very quickly
well in my case my Dad owns the Canadian Freight ways where we live so they're easy to get honestly though a lot of places are looking to get rid of them anyways and would be happy if you took them probably, beware though because the blue treated ones are heavy as f*ck, I mean like forty or fifty pounds a piece. The cedar ones are nice too but break more easily.