One gardening method I have found really useful when space is limited is the technique of square foot gardening. Pioneered by Mel Bartholomew in the 1980s, there are a series of books available explaining the tips and tricks to making Square Foot Gardening work for you, I recommend this one, the All New Square Foot Gardening book.
Basically, the system consists of using small footprint raised beds for your veggie gardening. By training your vegetables to grow vertically you can really squeeze a large crop into a relatively small area. The value of this is obvious if you are one of those people who has a very small yard! Some people recommend the use of Lasagna Gardening techniques when building small raised beds, but this is optional.
As well as being a great way to overcome space constraints, this ‘technology’ has many other benefits. Firstly, it is a lot easier to work a raised bed garden than it is to work the more traditional rows. Since they are raised you will find you do not have to bend so far to pull weeds, eliminate bugs, etc… Also, since they are relatively small, you can easily weed a significant fraction of your gardening space in a very short period of time.
Square foot gardening is great for companion planting too. Since everything is growing quite close together – the plantings are done in a square formation rather than a row – you can easily gain the benefits of companion plantings. For example, sewing a crop of carrots in your tomato bed will yield you a nice harvest of carrots before the tomato plants grow large enough to crowd them out.
Water savings are another plus. You quite simply need less water to water a small garden. Also, it is a lot cheaper to setup an irrigation system for a square foot garden than it is for row upon row of traditional gardens – the amount of hose and sprinklers needed is greatly reduced. If you go the irrigation route you can setup an automated watering solution, which can be very handy if you are as bad at remembering to water your vegetable garden as I am!