The program is called B&N managed accounts, and there's more to it than just selling Nooks.
They have in-store community managers as well as regional trainers, all of whom are there to encourage school and public libraries to buy Nooks. The libraries can get the Nooks in volume discounts, including cases and chargers. Not only that, B&N will also set up and configure the devices before shipping them.
After the sale, B&N supports the libraries with on-site training (once a month for up to 6 months) as well as email based tech support. A librarian can send a request to B&N and have a purchased title copied to a set of Nooks. They can also get Nooks shifted between the device sets simply by asking. This is a far cry from the other main library ebook vendors; 3M and OverDrive are set up to checkout one ebook to one device, so they cannot shift titles around like this.
Of course, one key difference between B&N and OverDrive/3M is that the latter sell ebooks under a library license while the former sells ebooks under a retail license. That is an important difference because OverDrive is limited to one user checking out an ebook at a time, while B&N's partner libraries can load the same title on to several Nooks (Adobe DRM limits it to 6, I believe).
Also, the libraries aren't supposed to be lending out the Nooks with the ebooks already loaded. I've been told by OverDrive that is arguably a contract violation, but I suppose B&N gets away with encouraging this program because libraries are doing the same with Kindles. As much as this might grate publisher's nerves, I think they'd rather see B&N get the sales than push more customers at Amazon. On the other hand, publishers might not know about it.
B&N hasn't been forthcoming about how many libraries are working with them, but it's not a small number. I've seen some indications that the figure is in the hundreds, and it might even have hit a thousand libraries by now. It's not much compared to OverDrive's 18 thousand partners, but it's not bad considering that B&N only launched the Nook in late 2009.
I've been meaning to write about this program for a while now, and given the recent ruckus over Penguin pulling their library ebooks, I really should have. B&N can offer libraries ebooks from HarperCollins, Random House, Macmillan, and Penguin - but without the restrictions (high prices & checkout limits) that 2 of the 4 put on the ebooks. That gives B&N library ebook content that you cannot get elsewhere. Nice, isn't it?
On a related note, B&N's library program might explain why OverDrive's app hasn't been approved yet for the Nook App Store. I've been told by Overdrive that it's been going through the approval process for a while now. I hope they're just impatient, because if B&N is stalling then they're cutting off their nose to spite their face.
A Nook Color which had access to both OverDrive and B&N ebooks would be very appealing to OverDrive's current partner libraries. They'd have their exiting content and the ability to add ebooks which OverDrive cannot sell them.
P.S. IF you're a librarian who is interested in this, contact your local B&N store.