I've found that the "SPMC" concurrency model tends to fit into my pipeline perfectly when I'm working on problems that need a specialized library like this. CK is for achieving unimaginably fast data-parallelism, like the kind you need when writing high performance drivers atop some DMA slab, or (in my case) using userspace networking to do something useful with millions of packets per second. Check out http://concurrencykit.org/articles/ck_hs.html for a better idea about just how fast this library aims to be (spoiler: tens of nanoseconds per op).
MPMC: ck_stack, ck_fifo, ck_ring (in the works), ck_disruptor (pending push), ck_bitmap (but not linearized) and ck_hp*
And in some cases, these are just building blocks for more complex structures.
Specialized: - Everything else, including ck_[r]h{s,t}*.
The synchronization primitives are all generalized to multiple writers (exception is ck_swlock which is specialized). The manual pages should point out bounded concurrency.