For those with tiiiiny gardens spend 15 minutes watching these two videos and be inspired....in my searching for information I happened onto these two videos at Youtube on Urban Permaculture Gardening.
This couple has 75 sq m available to grow vegetables and manages to grow 250kg of food per year which is much more intensive than agricultural land. Taking into account that they are in the UK and can only grow food from May - Oct this is a huge achievement. They use a combination of permaculture techniques, forest gardening and companion planting.
It's when I see something like this that I am even more inspired to use the space that I have available for growing food more effectively.