Technologies such as Google Earth and its rivals have proved a boon to archaeologists of all types. Many people will argue that sitting at home viewing satellite images is no substitute for going out into the field with notebook and camera, and they'd be right. However, aerial archaeology can save you a lot of time and effort.
My field of interest is Industrial Archaeology, or in other words recording as much as possible of disused and derelict industrial sites before the bulldozers move in and convert them to luxury flats. Often you will find locked gates and unsympathetic security guards, or the site you wish to study will be in a part of town that no sane person would visit with an expensive camera. For these reasons, being able to log in and (virtually) fly over the area for some hours is incredibly helpful. The high resolution images provided are good enough to recognise, say, a minibus from a car. You can pick out railway lines and even disused trackbeds from the lines of foliage or even just the disturbed ground. While doing this you are at no risk of a trespassing charge or being mugged by a gang.
This brings us neatly to another advantage. Previously, you would have had to find the owner and negotiate as diplomatically as possible for access to a site. Often you would fail, and frequently the repeated requests would make the owner less and less likely to allow groups to visit in future. Satellite imaging allows you to view a site without having to bother anyone.
Even if you are more interested in traditional archaeology, aerial photographs will prove a great help. No longer do you need to trawl an area on foot or in the car to spot sites of interest, you can trace many things easily from the comfort of your armchair. It must be remembered that the sites of villages abandoned after the Black Death in Britain were rediscovered in the 20th century after light aircraft became reasonably readily available. The famed Nazca Lines in Peru were first noticed by modern archaeologists in a similar manner. Aerial archaeology puts the ability to search for sites of interest into the hands of anyone with a computer and a fast internet connection. Combined with old maps, you can plot a route to a site or even use the software to upload coordinates to a GPS receiver. This will mean that instead of trying to work out where the old road went you will be wandering the precise location, metal detector in hand, and most likely digging up finds long before your colleagues have even found the neighbouring village. While public visions of "racing for the prize" are highly fanciful, in countries where the weather can be changeable and there is often little reasonable light being able to start digging earlier is a distinct advantage.