A few Black Friday eBook deals directly from their publishers/resellers.
Chizine Publications (fantasy & horror, mostly) has set their entire catalogue to $0.99 with the coupon code
RFD1113, good through midnight PST on Nov 29th.
Last I bought from them, they offered DRM-free ePub/Mobi/PDF bundles with a 5 download limit. And since last I tried logging into their store, they've changed stuff so that the old account info and order download pages don't work, so you'll have to contact their customer service if you bought stuff before the website change and ever want to see it again.
Angry Robot Books (sf/fantasy/horror) is offering 50% off novels and omnibuses from their own imprint, as well as the Strange Chemistry and Exhibit A publications. Use coupon code
robotfriday, good until midnight Hawaiian/Aleutian time Nov 29th. This is their
store page, and here's the
announcement on their regular website.
Last I bought from them, they offered DRM-free ePub/Mobi bundles, IIRC. Technically, you're supposed to be able to redownload them at any time, but something seems to have gone wonky with the order information page for my old purchases, where the links are supposed to be, so I guess that's another Customer Service support ticket I'll be filing.
Author
Diane Duane's Black Friday sale (actually for 50% off from the website page, unless that's a typo) is mentioned in
this thread here, and sf/fantasy titles by her and Peter Morwood are available.
For some bizarre reason, the epub/Mobi multiformat bundles are sold separately from the epub & Mobi individual formats, though they're all for the same price and it would be vastly more efficient for them to just sell stuff as a multiformat bundle anyway instead of cluttering the store with dropdown menus. You get a download link in your email which is supposed to be good for 5 or so uses, and occasionally they send links to updated versions when they fix the formatting and such. Their checkout coupon usage is slightly weird, so be sure to follow the instruction page on their website.
Dreamspinner Press (specialty m/m publisher, mostly romance but some mystery/speculative/other genre titles as well) are offering 30% off everything in their store through Nov 30th. No coupon required, discount is automatic.
They offer DRM-free ePub/Mobi/PDF bundles and their account info/download page is experiencing no issues when I look at it.
While I'm mentioning stuff, I'll note that specialty LGBT ebookstore
Rainbow eBooks, from which you may have purchased or gotten freebies from in the past, is shutting down, and says on their website that you will have until December 31st to grab all your stuff from them.
They don't seem to have sent me an email notice about it. 
ETA: It turns out they did send one, but it got buried under a bunch of other stuff, and came with a very brief 14-day limit to use up remaining store credit/gift certificate balances.
I suppose that's better than Fictionwise basically giving people no notice at all when it came to their remaining MicroPay, and the entirety of how BooksOnBoard handled their shutdown, IIRC.