I've been searching around the OpenDNS blog and website for clues, and I get their newsletters in the email, but haven't found anything directly related to PRISM or sundry. One thing they do offer that's security-conscious is
DNS encryption via their open-source DNSCrypt tool, which (IMO) gives them a shuffle over to the good guys side. Maybe we'll see a position post from them in the near future, I don't know. Until then I'll be keeping an eye out for any outside reports.
Also, if anyone here is using StartPage for searching, you may have
noticed their announcement of an encrypted email service they are calling
StartMail. I've signed up as a beta tester and now you can too:
Check it out here ->
https://www.startmail.com(p.s. It's not going to be free, but as f0dder and others have said; if it's free, you're not the customer, you're the product)