iTDL allows you to read and edit AbstractSpoon ToDoList (.tdl) files on your iPad, iPhone or iPod Touch. You just have to put them into your Dropbox, and iTDL reads them from there and saves them back directly to your Dropbox.
You need a Dropbox account to use this app! GDrive support and iPad version coming soon!
You can download AbstractSpoons ToDoList app for Windows here:
http://www.abstractspoon.com