I found out about TinEye a few minutes ago. It's a nice little search engine which allows you to find exact copies of a photo or even similar versions of it. You can either upload an image for comparison with their database, or point TinEye to a URL of the image you want to check.
The site is also used in Wikipedia for detecting the original source of uploaded images.
I know there is some other website which also allows similarity search of images, but I just can't remember the URL. Please leave a comment if you know of other such sites, thanks!
A very cool example of the so-called remix culture "happened to me" recently — one of the photos I posted on flickr was used as album art for a music CD, namely J. D. Warrick's "Going, a. The Leaving".
Btw., if you want to learn more about remix culture, Creative Commons etc. I can really recommend Larry Lessig's Wizards of OS 4 Keynote titled "The Read-Write Society" (OGG video: 144 MB, MP4 video: 224 MB).
(via One Stop Under)
On friday I stumbled over Photo Friday (heh), a nice site which posts a photo assignment every friday. Everyone is invited to submit photos which interpret the given theme. People can then vote on the submissions and six of them are finally listed as "noteworthy".
Oh, and I'm now listed on photoblogs.org, but unfortunately I entered the RSS feed of my photoblog there instead of just the URL. I registered with the site, claimed my photoblog and all, but I cannot change that #!&%* URL there. That has to be done manually by the admin(s) and even though I requested the change days ago (on the site and via email) there's still no response. Sigh...