Sadly, all of those are pretty inaccessible for screen reader users. Which is weird, seeing as Checkvist has tons of keyboard shortcuts. However, using the Tab key as a modifier is dumb because it's the key that, in any browser, passes from one link to the next. So I've never figured out how one can using tab+o to open some sort of window/menu/whatever. It's not a screen reader specific key, it's just a browser-based key.
I just looked at moo.do and I really can't figure out that page even just as they show examples on the homepage. is it flash-based?
I really want to love todoist, but it's iphone app and windows app are really inaccessible. And, if I could see, I'd love to use a mindmap. For being blind, i'm a surprisingly visual thinker. When I did all my music theory in college, I visualized the keyboard and constructed the SATB chord voicings that way. Same with phone numbers, I just see them in braille. But I digress.
I've been playing with an outliner thingy called Scribble. It's like a wiki with markdown syntax, but i really don't know much about markdown I think the site is
www.tryscribble.com but not totally sure.
So far, my most accessible outliner program on windows has been Keynote NF, which hasn't seen a beta release since a few years ago, 2013, I think.
I might try Gtdnext, just for fun. Apologies for the long post, but I do love testing apps for productivity software.