New studies of Hebrew language
Gabriel Birnbaum has published a study of the language of the Mishnah, based upon Genizah fragments. I like his method - instead of trying to deal with all the fragments together, he devotes a separate chapter to each manuscript under consideration. Only in the final chapter does he draw general conclusions from the material. Published by the Academy for Hebrew Language, table of contents here.
The second book is by Michael Rizhik, and studies Hebrew in medieval Italy. His study is based on medieval Mahzorim from Italy, and is published by Magness and Bialik (it's not on the Magness site yet).