www.coolmockups.com

Mainly commercial mockups but there are some free ones that you can use. The mockups seem to all be apple equipment.

medialoot.com

Design is easy with Medialoot. Unlimited access to fonts, icons, PSDs, templates, patterns, and much more.

This site offers some free resources that  generally need attribution but is mainly a subscription/commercial site. However the pric ...

www.psdgraphics.com

Download high resolution backgrounds, textures, and PSD icons for your web and graphic design project. You can use most of the media on this site for free but if you want to use them for commerical projects or emove the watermark you must pay $4 per it ...