This is still under development but sounds way cool. There’s a search engine on the way that will allow you to input a photo and will tell you what celestial objects are in the photo. Furthermore, the photo will be added to a database of sky images.
The site’s at Astrometry.net and it’s in really early alpha. There is a Web-based version of the search tool available, but at this writing it’s in closed alpha testing (there is an e-mail address available to apply for access.) There’s also a downloadable version of the tool you can get at http://astrometry.net/code.html . From the README file it looks like it’s Linux only.
You can get an overview of what the search engine is intended for at the project summary, check out the gallery of solved images (yow!), and, while you’re waiting for this project to get underway, browse links of related interest.
There is a lot of astronomy-language here; I think you’ll need to have a bit of background in it to get the most of it.