While surfing today I came across the blog "Kimi Kreations", today's tutorial was creating a chocolate filter for black & white images that is both simple and cool.
Kim has a bunch of other cool stuff on her site, be sure to stop by her blog.
Here is her chocolate filter:
1. Open your image in Photoshop
2. Create a new layer
3. Fill the newly created layer with brown (here is the hex code for the brown Kim uses - 3f2c02)
4. Change the blend mode to soft light
5. Reduce the opacity until you have the effect you like
Here is my before and after...