I've got Native Tongue on my shelf, which is notable for having a language embedded in the story that can be spoken. What else should I add to my reading list? I'm in particularly looking for books with developed languages, not just a few exotic place and character names added for flavor.
UPDATE: A language is well developed when it has a dictionary (or reasonably complete glossary) and reference grammar--or more likely--a few pages outlining how to string the words together.
(This question is copied verbatum from the Example Questions on Area 51)
This is now community wiki, I'm sure there will be more than one question that could be marked as the answer.