WorkFlowy is a lightweight outliner endorsed by Matt Cutts
WorkFlowy is deceptively simple. It's just an outliner – a list-maker! You click on a new line, write whatever you have to write, and hit Enter. Done – you now have a bullet, a "to-do item," or whatever you want to call it. Hit Shift+Enter, and you can add some text as a note for that item.
There is nothing revolutionary about it, except for one key difference: it lets you drill into items. By "drilling in," I mean that you can click the bullet next to an item (or press Ctrl+right arrow), and you're then transported "into" the item. You no longer see the whole list – the item you've selected becomes the "master item," and it looks like it's the top of the hierarchy.
This simple difference makes it possible to forget that you have a huge list of other items. It makes it possible to use Workflowy for managing a whole bunch of disparate projects, thoughts, and whatnot. Workflowy was intentionally kept simple -- there are no "tags." You can't send links to specific items. There are no collaboration features. It's a very single-minded tool, and it just works.
I've promised you Matt Cutts in the title, so here's what Mr. Cutts had to say about it, according to WorkFlowy's homepage:
"Workflowy has become one of three tabs that I keep open in my browser, along with Gmail and Google Calendar."
That's a powerful endorsement if I've ever seen one. There's also a short video about Workflowy after the jump.