I posted this in the iPhone app forum but since it works on my iPad I thought I would post it here as well:
I don't know if this is still working but my local news station was offering the iMap weather radio app for iPhone for free yesterday. It does work on the iPad but you will have to send the text and manually enter the link replied into Safari then manually enter the code and redeem the free app in iTunes
Copied from the news channel's FB page:
You can now get the News On 6 iPhone Weather Radio App for FREE by texting TRAVIS to 79640. It’s usually $9.99, but we’re making it available for free!
Text TRAVIS to 79640. When you get the text, scroll to the very bottom of that page and you'll see a "capcha," where you have to enter the words you see on the screen.