FilmDev is a website that tries to answer the question:
"What will film X developed in developer Y look like?"

Here's how it works
1. Sign in via Flickr.
This is a quick process and simply gives this site (FilmDev) access to your Flickr photos for ease of tagging when creating a recipe.

2. Create a "recipe" describing what film and developer you used and adding any other details.
You may also browse and comment upon other user's recipes.

3. Tag your Flickr photos that were developed with that recipe.
This can be done through the FilmDev interface or of course directly via the Flickr site.
About the site
Site developed in Ruby on Rails using Vim by Darren Greaves (boncey on Flickr).
Creds to Richard Jones for design advice and the FilmDev logo.
Support and contact
There is a FilmDev support group on Flickr where you can go to ask any question about the site or get more info.
To contact me privately please use the contact form on my blog.
FilmDev blog
There is a blog on Tumblr for occasional news and announcements about the site.
Twitter
FilmDev is now on Twitter - new Recipes, Films and Developers will be posted along with occasional news about the site.
Greasemonkey script
There is a Greasemonkey script to parse a Flickr page for the 'filmdev:recipe' tag and add a link to the the recipe on this site.
It's very similar to how the Upcoming links work (See screenshot here).
Note: You'll need Greasemonkey too.