Welcome to Gaia! ::

surprised And I read this 3mins before the internet gets switched off! gonk I'll try and get something done quickly, and swipe it back on... ninja

Why so urgent?

Eep! I nearly forgot.

http://www.sxc.hu/
This one might be a little slow in loading the first page. It's the best one for non-watermarked high resolution photos.

http://www.inmagine.com/
Not the best for photographs, but has video clips and illustrations too.(I mean, look at this! http://www.inmagine.com/view_image.php?queue=119&filename=pdem004016&dpi=300 Muahahahaaaaa!)

http://creative.gettyimages.com/source/frontdoor/DefaultRfLanding.aspx?country=gbr
I personally find this one gives the best results, as the search tool and keywords are obviously really well thought out, and is very specific. You can't get very high resolution photos though, so for art uses, it's not so great, but for graphics for use on the web, it's fine. Each page of thumbnails takes a while to load.

http://www.image100.com/index.php
Again, you can't get the images in very high resolution for free here, but they're big enough for my purposes.

For all of these, you have to sign up because the uses of the images are limited. (the biggest one; not allowed to use to re-sell)