I discovered these free science and social studies units last year, and they are great. Published by the California Education and the Environment Initiative, each unit is centered within the context of the environment. They're aligned to the California State Standards for science and social studies, so you could use these instead of your textbook series at different points in the year for many of the standards. (I don't know about you, but I am not in love with my science textbook or my social studies textbook.) And, the best part is that they've recently released Common Core Correlation Guides for each unit, making it totally easy to include the Common Core standards in your lesson plans.
The website to download these units is www.californiaeei.org
The website will ask you to register your email, etc. to get the password for downloading everything (at least you needed to do this last year), but the password is teacheei if you don't want to go through all that.
