For a rich, thorough treatment of the subject, with a good balance between computer science and practice, I recommend The Art of Multiprocessor Programming. A lot of examples are in object-oriented code, i.e. Java, with other languages scattered throughout. It just depends on the topic being covered. What I really love about this book is that it discusses how common algorithms should be implemented in a concurrent design. Of course, there's so much more!
For general concepts and a treatment of pthreads, I really like Programming with POSIX Threads. Being the library and API that it is, it's in C.
For Windows and C# developers, check out Joe Duffy's blog. Joe works on parallel libraries, infrastructure, and programming models in Microsoft's Developer Division. He has a book coming in Nov. 2008 titled Concurrent Programming on Windows (Amazon link).
Also, don't miss the Godfather's blog: Herb Sutter's Sutter's Mill. He has links to all his articles in Dr. Dobb's Journal and more. Click his Concurrency category.