I currently use Things as my general, all-purpose, powerhouse to-do app, but for those of you who aren’t as savvy on shelling out the 50-odd clams or so for a full-on GTD system (though it does come highly recommended), NowDoThis might be the perfect, free, web-based alternative you’ve been looking for.

The interface is ridiculously simple – just type out a short, concise list of the tasks you need to do at the moment, and upon hitting ‘save’ the app will display the topmost to-do in a nice, large font until you hit ‘done.’, whereupon the app will then display the next item in the same manner, ad infinitum (or at least, until you reach the end of the list).
What’s also nice about the app is that by displaying only one item at a time, all other potential distractions you might get from your other tasks are virtually eliminated – your focus is set on only one task at a time, allowing you to put your mind to working on that single item with all your available attention.
And of course, it also remembers your tasks via your online history, so even if you quit your browser, all your to-dos will still show up the next time you visit the site. Just don’t count on them still being there if you clean out your cookies, though.
Finally, here’s a little video from Revision3 demo-ing the app, so that way you get to see it in action first-hand. Well, third-hand… but you get what I mean.
For more advanced functionality and other news regarding the app, check out the NowDoThis blog.