TaskPaper, a list management application from the author of WriteRoom, was recently updated to version 2.0. Back at version 1.0, it was an instant favorite among some TUAW bloggers. Beyond simple list management, it's really a very full-featured task manager which revolves around the idea of utter simplicity. It uses plain text files which become easily-navigated, well-formatted project and task lists within the application.
I've always appreciated plain text lists for their compatibility with, well, everything. They're malleable with just about any scripting language, copy and paste-able into everything from mind maps to online documents, and ever so simple to edit (I also had a lot of fun with the GTDAlt bundle in Textmate). Despite being loaded with new features, TaskPaper 2.0 maintains everything there is to like about working with plain text lists.
If you like AppleScript, though, you get an extra boost: TaskPaper's new AppleScript dictionary is brimming with classes and elements which alleviate the pain of AppleScript text manipulation. You can quickly and easily find tasks, grab selections, add and remove tags and more. Like Things, TaskPaper has an extremely flexible tagging system (including the addition of values to tags, e.g. @priority(3)) which, with or without script-fu, allows you to create a system which works for you.
The 2.0 release also improves on the interface, and brings those plain text lists to life with user-configurable styling. The new search syntax allows for complex searches based on projects, tags and tag values, in addition to text content. The drag handles and shortcut keys also add a level of elegance to the editing and use of your text-based lists.
You can try TaskPaper out for free, or pick up a license for $29.95USD. As further proof of my "compatible with everything" claim, check the bottom of the TaskPaper page for a list of compatible projects for Vim, TextMate, BBEdit, online task managers and even... Windows (sure, why not?).