There will be times when you need an image for a project. Perhaps something to fill a space or illustrate a point on a website. Perhaps to enhance a print project, client presentation or e-mail announcement.
If you have the chance, commission a photographer so you can get exactly what you need. Sometimes that just isn't possible, either because of limited finances, deadlines or geography. So, try one of the online image libraries which are packed full of material from excellent photographers.
Many of them offer images at remarkably reasonable rates (some less than £1 or $1) and, not only does the site make money, but they also give a cut to the photographer. Interestingly, some of them will give you free images just to encourage you to look around their site! Always credit the photographer and agency and make sure you check the extent of what they will let you do with the image.