DIY concrete fire pit bowl from eHow. Summary: Make sand 'hill' in size you want bowl to be and, using a trowel, cover sand with layers of concrete, smooth a flat bottom to sit it on and vent holes, letting dry slowly under plastic sheet. Invert when dry.
diy Hypertufa: a mixture of Portland cement, sand and peat moss. If you want you can replace the sand with perlite, it makes the pots and trays a lot lighter as perlite weighs almost nothing. Tufan takes a little longer to harden than ordinary concrete.