Get the cheapest tank you can get, some old nasty thing off craigslist that's past its expiration, then take it to homedepot for swap (pick out the newest tank they have). From there on out take it to a place that does fills. I would avoid Blue Rhino, if you look at their fine print you'll see that they don't do complete fills anymore. With rising costs they decided to keep the price the same but reduce the amount of propane. New Blue Rhino tanks are also starting to come with a proprietary/magnetically activated valve that cannot be filled by anyone else (called Tri-Safe II valve).
From the Blue Rhino site: