All good ideas above. I'd be tempted to stay away from the bags of firewood from the local shop as they are usually ropey softwoods that are awful to turn and I wouldn't want that to put you off turning!
Stick to hardwoods. Don't pass a skip without looking in. If you see anyone having an Indian sandstone patio laid try to get hold of the crate they are delivered in, they are made from lots of good hardwoods, mainly eucalyptus. Some pallets are also great hardwoods.
With a lot of the advice and good ideas here I have picked up a few bits and bobs to have a go at now. The firewood is going where it belongs, on a fire. I have picked up a pack of 50+blanks from ebay at a nice price. If I do find any little treasures in it then I just hope I can identify what it is.