We are testing integration with Evernote via Zapier: https://plus.google.com/b/114021845786371597651/+Checkvist/posts/SoiDZevJKdZklw commented
It's easy to link to Evernote. Just open the Evernote Notebook or Note you want to link to and copy the URL, then paste it as a task or note in Checkvist. You can store all your project reference and checklists and so on in EN, and see them with one click from within CV. The only (very small) drawback is that the URLs are ungainly.