Was looking to pick up a couple of extra propane tanks for my RV and patio heater and ran across 3 at my local Wal-Mart for $21 each on clearance. YMMV of course Link [walmart.com]
for the areas around me show zero on hand, although I know that isn't the case. Not sure what is going on with that. The Walmart webpage does seem to show some in stock in some of my local areas however.
Edit: This tank is empty (does not include propane). This deal is best for those of us that have a refilling station nearby and opt for that instead of doing exchanges. As several have pointed out, if you can find a cheap (or free) bottle on Craigslist, you can then take it to an exchange point (Blue Rhino) and get a newer bottle as well.