<p>I understand the mantra of "don't roll your own" when it comes to site security frameworks.</p>

<p>For most cases anyway.</p>

<p>I'm going to be collaborating on a site that integrates text-messaging into the system.</p>

<p>I'd like to use an existing, well-tested security framework to protect the users data, but I need it to also protect a users phone number as well.</p>

<p>I wouldn't want to be the one responsible for a list of users cell phone numbers getting jacked and spammed.</p>

<p>What suggestions can the community offer?</p>

Since you need to be able to retrieve the phone numbers, the only thing you can really do to protect them (beyond the normal things you would do to protecting your db) is encrypt them. This means that you need to:
Make sure the key doesn't leak when you inadvertently leak a database dump.
Make sure your system doesn't helpfully decrypt the phone numbers when someone manages to SQL inject your system.
Of course the recommendation of not rolling your own still applies, use AES or some other well respected cipher with a reasonable key length.