I’ve used lots of tools to manage my to-do list, but I’ve never found one with the perfect combination of simplicity and features. But iGTD 1.4 comes awfully close. Though it’s based on the Getting Things Done productivity system, you don’t have to be a GTD groupie to use it. Like most to-do software, iGTD lets you sort tasks by project, priority, and due date; like GTD, it also lets you group them by context (where or how you’ll accomplish them). You can tag items with keywords, URLs, and contacts, and a menu-bar tool lets you quickly convert e-mail messages and files into to-do items.