Take some old Pallets + unused space + soil + seeds = raised bed!
Soil, Volume (m^3) = Area of raised bed (m^2) x Depth of bed (m)
The most practical design I know is:
1. Put a plank of wood (ripped off the old pallet) long side along the ground like standing on its edge.
2. then you put pegs either side to hold it upright
3. then fill with soil.
looks good, works great
takes like 2 hours tops
Old Pallets: http://picasaweb.google.co.uk/lh/photo/Mr8m5VJ_5-aaJSAzQwsnXQ?feat=directlink
Proposed Site: http://picasaweb.google.co.uk/lh/photo/AZd9OLyNTSu1dwrLYpD8PA?feat=directlink