SL3 has RTMed and Laurence Moroney continues his SL series that will update your skills. It’s based on the SL beta but it’s still valuable. I suggest you browse at your local bookstore with your favorite mocha at your side and see if it meets your needs. For those that are interested, there is a free downloadable copy that discusses only the new features (sorry, not the whole book). You can download it here. I recco the free download to get up to speed on the new features.
For those not yet on SL2, here is a developer book I highly recommend:
For the SharePoint developer, here is a great book by Steve and Paul. I’m told there won’t be an SL3 version, but maybe SL4????