This is a monstrous review article on quantum entanglement. It is 78 pages long!
Abstract: From the point of view of quantum information science, entanglement is a resource that can be used to perform tasks that are impossible in a classical world. In a certain sense, the more entanglement we have, the better we can perform those tasks. Thus, one of the main goals in this field has been to identify under which conditions two or more systems are entangled, and how entangled they are. This paper reviews the main criteria to detect entanglement as well as entanglement measures and also discusses the role of entanglement in quantum communication and cryptography.
Even if you can't read the whole thing (who can?), at the very least, the wealth of references is more than ample reason to keep a copy of this thing.
 Horodecki et al., Rev. Mod. Phys. v.81, p865 (2009); the ArXiv version can be found here.