Under pressure, deadline approaching or you just need some graphics for a mockup, good stock can be a real time saver. Here is a list of websites you should be bookmarking.

Photography

stock.xchng
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One of the biggest and probably most popular stock photography websites out there

MorgueFile
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Some truely amazing stock photography can be found at MorgueFile, a must visit.

Unprofound
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Filter the desired stock by colors, no registration needed. Nice and easy!

Public-Domain-Photos
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As the name already says, very uncomplicated website to find the stock you need.

PSDs

365 PSD
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One Free PSD a day, what more can you ask for.

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Premium Pixels
High Quality Textures, PSDs etc. from the very talented designer Orman Clark


Random

Smashing Magazine
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The well known online magazine "Smashing Magazine" is publishing Freebies on a regular basis. From icons to complete templates, you name it.

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Web Design Leder
Not always completely free but nonetheless a great resource, especially for webdesigners.


I will surely update this list in the future. If you have any suggestions let me know!