LearnZillion is an online database of short video lessons that address learning topics aligned to individual Common Core standards.
Scoutlier is a warehouse for middle and high school students to share pictures, observations, measurements, or videos (either on the web or through iOS and Android apps).
National Geographic's Open Explorer site is a digital field journal where explorers of the world (or just their backyard) create and go on expeditions and share their stories along the way.
826 Digital is aligned to the Common Core ELA standards but can also work for writing programs in states with their own standards.
Workbench is a PBL platform where students can complete STEAM tasks using everything from basic art supplies to technologies such as Sphero, Makey Makey, Raspberry Pi, and more.