This is a great chart from Kathleen McClaskey and Barbara Bray showing some of the differences between differentiation, personalization and individualization. It's a great resource for educators who are looking for ways to do any of these three things with their students.
Tools for Differentiation - helping teachers meet the needs of all learners
Differentiation - tools, tips and resources
Differentiating with Web 2.0 Technologies
Great LiveBinder on Differentiation for High Ability Students
Differentiator - free web app to help teachers differentiate using Blooms Taxonomy