HDR maps are good for making very realistic renderings using rendering programs such as Yafray. HDR stands for High Dynamic Range. HDRI stands for High Dynamic Range Imaging.
The following are a list of places on the internet where you can download free HDR maps:
However, if you want some paid ones, you can try here.
Hope that this is useful. 🙂
If anyone is looking for studio style HDRI maps check out:
http://www.studiohdrimaps.com
We specialise in studio .hdr maps for light coves, lightboxes, softboxes etc… Perfect for industrial and product designers who want to replicate photographic situations for 3D product shoots and renders.