They phased those out ,sold what ever inventory they still had, and are concentrating on the HD tablets now. Didn't realize it either until someone else mentioned they were no longer on the website, shortly before I purchased one for one of my kids.
Yeah, they are now phased out.
A -quick-comparison of the NT vs the HD
Both are 7 inch screens, but the tablet is a heavier device with less resolution.
They have about the same battery life (10hrs w/ WiFi off)
I believe the CPU in the HD is a newer generation than the one in the NT. It certainly feels faster.
The HD has all the software features of the tablet, but also has profiles so you can share your nook with family/friends and not see their books/apps/movies also you can limit kids access to various things on the Nook. BN Video, rent or buy movies from B&N with the option to stream or download the content. Scrapbooking, you can pull pages from magazines, newspapers, etc and add them to a scrapbook.
As an aside, if you purchased the NT recently, I believe November 15th but don't quote me on that, you can exchange it towards a Nook HD. It may be in your best interest to do so as the cables for the NT/NC are less than amazing and will eventually become rather difficult to find.
I have a NT, and while I wished they preserved the web pages, try Googling "Wayback Machine". It's an Internet archive. I bet you can find the pages there. I did for Apple's iPod touch because I have the 3rd generation and I wanted a nostalgic feeling of remembering when I looked at the web wishing for it. (It makes me feel better about mine instead of the shiny new ones.)
I'm used to technology phasing out faster than you can talk. It's just a part of consumerism and life in America. My iPhone is obsolete basically, so is my iPod, and my NT. It's a "whatever" factor to me. I may want the new devices, but if I have working ones, why bother looking? Sure they're shiny, but I have working devices.
I only disagree with myself here because I really want Nook Video Service. I doubt that's going to happen. Sideloading is hard for me on a Mac (I have Handbrake but I hate it, I wish DVD Catalyst had theirs for Mac). Buying videos so I could watch them anywhere? A win. 5ivedom's comments have me hoping.
EB613, you should let the DVD Catalyst people know. My understanding is that they could probably keep a lot of the core code and just do the port of the UI and some parts to make it work for Mac.