What's a good sub-$500 tablet with stylus input?

I'm looking for a table about the size of a Nook (6" screen or so), that runs android and accepts pen input. Basically, would love to replace all the little pen/paper notebooks I have to carry with something that I can sketch in, and then save as a PDF. Likewise, it must be able to read PDFs. Not worried about connecting to any networks, basic wifi would be cool, but not necessary. Any info would be appreciated :)