The Good:
The Evil Genius created a nice Spanish-English dictionary for the Kindle ebook reader:
http://www.evilgeniuschronicles.org/wordpress/2010/01/07/my-free-and-open-kindle-formatted-spanish-to-english-dictionary/
The Bad:
The dictionary is just what I was looking for to improve my Spanish. Unfortunately, it was created for Kindle 2, which uses only one dictionary at a time. When using it on a Kindle 4 (which manages one dictionary for each language), it can be selected for English books only, which makes it pretty senseless.
The Solution:
The actual problem is the missing language meta data of the dictionary. After several unsuccessful attempts to change the language meta data, I discovered the Java Mobi Metadata Editor: https://github.com/gluggy/Java-Mobi-Metadata-Editor
It is easy to use and lets you change the "dictionary input" and "dictionary output" language meta data. Thus, the dictionary now works on my Kindle 4 and the Kindle Touch. If you're also interested in the updated version of the dictionary, you can download it from:
https://docs.google.com/open?id=0B-iHdfk93LueT0c2WmUyWHdQTjQ
