I'm making a post here to let people know about this library, since I think it may be useful; if such a post is inappropriate or offensive, please let me know!
liblfds is a portable, license-free, lock-free data structure library, written in C.
The library has already been ported to a number of platforms (Windows (user-mode and kernel), Linux, IA64, x86, x64, ARM, GCC, MS C compiler, etc).
Release 5 was published late last night :-)
Right now there's only a few data structures - the queue and ringbuffer are the most useful - but a *lot* of work has been made into making the library accessable; there's a blog, forum, wiki and bugzilla on the web-site and a metric *ton* of documentation.