freepik.com and hosted by mightydeals.com.
This collection provides the patterns in .ai, .eps, and .jpg formats, and the vector formats are fully editable. What's even better is that they’re all free for personal and commercial use, all you have to do is credit freepik.com.
It does require you to sign up for their newsletter before providing you with a download link. But you can easily opt out of the emails later.