The preprint Three Lectures on Meson Mixing and CKM phenomenology points out that certain neutral mesons (including the neutral K meson) mix with their antiparticles. This was a big surprise to me. It's odd enough that particle/antiparticle states don't usually mix, but there are exceptions to that rule too!
Note that many neutral antiparticles don't mix because of other conservation laws, neutrons and neutrinos obey baryon and lepton number conservation, or so it seems.
See also Status of CP Violation for another fairly recent review.
Here's another very recent preprint: Flavor Questions for the LHC
The physics underlying quark and lepton masses and mixings (the "flavor problem") is the least well understood aspect of the Standard Model. Some questions of flavor physics, and ways in which the LHC can help shed light on this problem, are described.
Flavor Physics in the Quark Sector is another recent summary of quark mixing and CP Violation experiments and theory.
