Finding the right image for your blog post, brochure, or graphic project need not be expensive. Now admittedly, if you have lots of funds to support your graphic design needs then searches on stock photo sites need not be a complicated task. The more restricted your budget is the more challenging it can be to find images to use. 
I always start my search for images at sxc.hu, a site called stock.xchng. Until recently it was an independent site, but it has recently become part the vast Getty Image empire. The site is still comprised of user submitted material to which the copyright holder has control over usage rights for each image.
The most important feature of the site, beyond the huge n
umber of images available, is the powerful search function that allows for up to three keyword searches, a subject category, restrictions on use, image size, photographer, and type of image. The search I always start off with is a keyword with no use restrictions. With just a bit of honing of search terms, I can nearly always find an image the will enhance my post or fill my graphic need.
I heartily encourage use of Stock Xchng.
Even though many photographers do not ask for credit, it is always good to give a link back to the photographers work and let them know where you have used their work so that, if desired, they can show that their work is being used. Helping the photographer build a client list, so to speak, is a great way to thank the photographer or graphic artist for providing work that fits your needs.
Some of my favorite images from the site those used in this post.