Lumber yard, demolition sites, construction sites, busted up furniture from the dump and or second hand stores, your yard, the neighbor who just trimmed his fruit trees, side of the road, that ugly stump your aunt has been complaining about the dead stick that was too cool to throw in the camp fire, plus several others......and thats just for wood!
Old bowling balls, plastic boxes can be cut up and segmented, vinyl records from yard sales, plastic tool handles, old Corina counter tops ask one of the local kitchen remodeling companies they usually have piles of scrap laying around......and thats without casting anything. Buy yourself a jug of PR and you can literally make blanks from moose poo!
Or you could just ask here! I think most of us have sent a new turner a box of wood at one time or another.....including myself.