A list of useful resources where you can find free stock images for your projects:
Freepik – vectors, PSD, icons and photos
Stock Repository – a Flickr group that provides images made by their users
Foter – a search engine for stock photos. You can sort images by categories
RGBStock – it provides a great number of high quality stock photos, you must login for download (within the same site or a Facebook account). You can search them or surf between new photos, popular, random
26 places to find free multimedia for your blog even if the article is dated 2009 it’s a great list of sites from Mashable where you can find free stock
GettyImages a stock site that also offers royalty free images
Everystockphoto stock photo search engine