Typically Apple's Black Friday is a late thing, not an all day thing. They do it from like 6-midnight. Though I think they have done it all day too.
In past it has been stuff like 10% off any Mac, Airport Express $99 (reg. $129), $20-30 off iPods, things like that. They will try to have a theme to it. Expect them to push iMacs, MacBooks, iPods, iPod Hi-Fis will most likely be in sale (maybe $299 or $319).
As far as memory, I would be absolutely shocked if upgrade RAM was on sale. Apple will focus on new items, and while iPod accessories may be on sale, everything else will be tied in to bigger purchases. And their deals on Macs are never any better than an EDU discount at best (and no, they can't be combined).