I was lucky enough to find one on Craigslist. It was still in brand new unopened box, with shrink wrap even! Guy was asking $230, I negotiated him down to $200. Met the guy, didn't have correct combination of bills/change, so ended up giving him $197 cash. I'm writing this on it now.
I found eBay to be selling for almost the cost of new. But keep your eyes peeled there, follow listings, as well as monitoring CL. These just came out in Nov. or so, so there are not a lot out there used yet; and it's too soon for refurb units (look for those come Feb. maybe?). OTOH, some people may have gotten these for gifts for Christmas, and decided they would rather have the cash instead (for example, my guy was under-employed and working on completing his Master's degree). So there might be a few deals out there right now, be on the lookout!
And finally, not sure what your time frame is, but when that new 7" Acer Memo comes out (it was just announced today or yesterday at CES, but who knows when you might be able to actually buy one), B&N may lower their price, or (more likely IMO) people may start selling their NTs and buying instead the Acer Memo. If you haven't heard about the Memo, it's the same 7" screen size as our beloved NT, except it will have a quad core Tegra 3 processor @1.2 gHz (or thereabouts) along with GPS, BT, cameras, a SIM slot (although as of this writing, no carriers have announced any plans yet) and running plain ICS (in short, a "real" 7" tablet) for the same $249 as our NT is selling for now! And that will be some stiff competition indeed for B&N.
So whatever you decide to do, good luck, and happy hunting!