Basically, all of the following free stock image sites provide contents for both personal and commercial use. Except Unprofound and FreeMediaGoo, almost all of them require a link back to their website. SXC and flickr have the largest collections, try your search there first.
SXC – SXC is one of the best alternatives for expensive stock photography. Most of the images fall in the “standard restrictions” category, i.e. you are free to use the images on websites, multimedia presentations, and etc. As a general guideline, SXC suggests that you should always ask permission from the photographer if you plan to use the image in a website template, printed reproductions, or “print on demand” products that you intend to sell.
flickr – Many Flickr users offer their work under a Creative Commons license. Under their advanced image search, you can specify and only search within Creative Commons licensed content, find content to use commercially, or modify, adapt or build upon.
Image*After – Image*After is a large online free photo collection. You can download and use any image or texture from their site and use it in your own work, either personal or commercial. You can even redistribute or sell their images and textures altered or unaltered as part of printed work (e.g. posters, cd-covers, and etc).
morgueFile – Looking for high resolution stock photos for your design needs? Search Morgue File for free reference images. You are free to adapt the work, use the work for commercial purposes, or use without attributing the original author. You can not sell, license, sublicense, rent, transfer or distribute this image exactly as it is without alteration, and you may not claim ownership of this image in its original state.
Freerange Stock – Just sign up for a free membership, log in, and download high-quality, high-resolution free stock photos and free textures. All images are at least 2400 x 1600. License Summary: You can do nearly anything with the images, commercial or not. Just don’t redistribute them – this means don’t host the images or repackage them, just post a link to this site and let others sign up download them. You cannot offer image for sale, or offer images as part of printed products.
Unprofound – Over the past decade, Unprofound has grown into a global collaboration of photographers. It is 100% non-profit. You are free to use the photos in both your website design and any video productions your company creates, non-profit or otherwise. You are not required to credit, display copyright or return a link to use the photos there. If you choose to do so, you can credit either the unprofound.com website or the specific photographer(s) responsible for the photo(s) you use.
FreeMediaGoo – The images may be used for commercial or personal use in print, film, TV, Internet or other media. Credit for the images is not necessary.
PhotoRack – All photos at PhotoRack are Free to use for personal and commercial projects. No limitations & No backlink required to use them.
FreeImages – FreeImages has more than 6000 free stock photos in 84 categories. When an image is used, a credit link to their website is required. Acceptable credits include ‘image: www.freeimages.co.uk’ or a hyperlink to the URL ‘http://www.freeimages.co.uk’.
Free Stock Photos – Free Stock Photos provides free and high quality stock photos for your personal or commercial design projects. Credit for the use of materials downloaded from this site such as a link back to Free-StockPhotos.com is much appreciated. Here is a suggestion format: Image by Free-StockPhotos.com.
FreeDigitalPhotos.net – Attribution is required for free image download. For example: “Image courtesy of [contributor name] / FreeDigitalPhotos.net”. If you prefer non-attribution or bigger and high-resolution image, you need to purchase the image.
FreePhotosBank – Any photos/pictures posted by the author “freephotosbank” are free to use as long as you are using them for a website, book, magazine, etc. To use their photos/pictures you must accredit them on the work that you used the photo/picture on/in for the use of them.
FreePixels – Images and digital creations downloaded from their website may be used for both personal and commercial purposes. Every Freepixels image or digital creation used must retain the domain name: freepixels.com when used on the internet.
Pixel Perfect Digital – Pixel Perfect Digital offers free stock photos, backgrounds and textures. All their images are provided under a Creative Commons Attribution license. This license lets you remix, tweak, and build upon their work, even commercially, as long as you credit pixelperfectdigital.com for the original creation.
Dreamstime – If you are a designer, there you can download high resolution Royalty Free stock images for free.