A useful starting point for imagery is
Flash Earth ...satellite and aerial imagery of the Earth in Flash - you can find the area you want, and flip between Microsoft, Google, Yahoo, and a few other of the online providers. Google and Microsoft are far ahead of the others, but between them which is best depends on the area you're looking for.
In theory Google should be getting much better imagery soon. A few months back the company which provides much of Google's imagery launched a new satellite with higher resolution than what's been available (from satellites) before, and once Google start getting that it should be better resolution and more up-to-date over larger areas.
David