Theres a great thread on the budget board about Nooks. I personally have the 3g Wifi Nook, not the Color Nook but I love it. There are tons and tons of free books out there on the Bn.com website. Heres the website:
http://www.barnesandnoble.com/u/Free-eBooks/379001668/?start=43&cds2Pid=29905
You can also search on the Nook with a 0.00 price and hundreds of thousands will come up.
Today is Friday, so there are two new free books just today for the Free Fridays promotion. Free Fridays are books offered for free for one week only.
You don't need a BN.com card at all. All you would do would be to set up a BN.com account (if you don't have one now) and that is it. you can purchase books directly from your device. I've only bought one book and it was easy to do. -just use a credit card.
I would recommend getting a cover. I bought my Nook cover at
Amazon (of all places) Once I got the cover I was pretty much set.