If you’re running a print campaign, re-designing your website or anything else that is central to your business then use paid for stock imagery.
However if you need an image for a blog post or something similar, free stock photography can usually offer something interesting. If you can let the photographer know you have used their image, they usually appreciate it. A link to the image is even better. Below is a list of my go-to selection of free stock image sites, this is by no means an exhaustive list but these sites have been the ones that I feel have offered me the best images when searching.
Stock.xchng – Probably the most well known of the free stock photo sites, it is owned by Getty Images and is powered by the iStock photo team. This has probably the highest standard of images on the free stock sites. It’s also worth checking out their tutorials section, there’s nothing earth shattering in them but you can certainly pick up a few tips for image manipulation.
Free Range Stock – An interesting concept, photographers who submit their work here get a cut of the advertising revenue from the ads on their images page. This does mean there is quite a bit of advertising on the site. I guess the idea is that it will attract more professional photographers with the monetary incentive, although I’m not sure this is actually the case (I mean, does anybody really make decent money off a few AdSense ads, especially when thats split across the entire userbase?).

Stock Vault – This is part of the Curly Eskimo Communities selection of sites (a selection of design sites, with a slight emphasis on free). The site has a good selection of stock images, it’s not as extensive as some of the other free stock sites but the quality is always high.

Pixel Perfect Digital – Seems to be mainly amateur photographers uploading their pictures. The search facility isn’t brilliant, however the site is well structured, so if you’re looking for a general abstract picture this can be a great place to get inspiration. There are some very good photos on this site but there are also some fairly poor ones too (not sure what the approval/moderation process is, it’s not outlined anywhere obvious). The site has a fairly small collection too, that said the site can be very good for textures and illustrations.

Morgue File – A morgue file (in design and digital art terms) is a file that holds all of the images used in a design for reference once the design process is complete. There is quite a large selection of good quality images here and it is easily searchable.