Without a doubt, the most useful reference tool I use when planning CCSS aligned technology powered learning experiences is Common Core, by Mastery Connect.
I have the widget installed on my websites and wikis. I have the app on my iPad and iPhone. I use MasteryConnect when designing learning experiences to provide me with quick and easy access to snippets of the information I need. With that information at hand, I can fine-tune the learning experiences I design to target skills necessary for success in school and beyond, as identified by the CCSS.