Ideas for Differentiating - PBL Ideas (Love this chart. The lesson is good, too, but the chart is what I'm pinning for Project-Based Learning
What exactly is differentiated instruction? A handy infographic from @officialascd helps explain.
March 2015 Blog Post from Science and Math with Mrs. Lau. Good stuff on differentiation, good links, and good freebies.
How to Differentiate Instruction in Mixed-Ability Classrooms. Fantastic introduction to differentiation. Just over 100 pages: Quick, EASY read!