Seems too good to be true, but it is, RingPlus will give you free cell service, ad supported during the outgoing ringtone. You don't loose any time and it is really free cell service. There is a initial top up fee that most plans have, depending on when you sign up there are different promos running and you better have an unlocked Sprint capable phone ready to do this, or sometimes they might have some inventory to sell in their store or Classifieds but these phones are not as great as what you might get on eBay. Just last week there was a Nexus 6 for $180 on eBay. You can order SIM cards from Sprint.com right they will work on RingPlus, or they also have them on eBay. The setup is easy, if you have a compatible phone, just enter the ICC ID and IMEI on the RingPlus website and service can be running in minutes. There is a higher tier of Member Plus where you get some extra services like support, otherwise you can pretty much find all the help you need by googling the forums and it is a community of users helping other users. You are expected to do social media to spread the word, which I guess I am doing right now.
Anyhow all in all it is a great deal if you don't mind listening to a short ad until someone answers the phone. If you have good Sprint coverage where you are going to use this, it should work great for you. On the downside the voice calls have some lag and are not of the highest quality, however are usable. You can also connect your SIP phone to the ring plus number for more calling possibilities.
There is a history of the company and a WikiPedia page now, based Karl's post, "RingPlus grew from 5,000 to over 91,000 subscribers in a year ",this is the fastest growing carrier in the country right now.
2/21/2017: Update, our accounts were moved to Ting with a $35 credit. So my first sentence stands, it was too good to be true we didn't meet the target of 500,000 users to get the ad inventory.