Tasks Pro: A solid web-based task manager
If you're into managing your task list online, there are many options these days. It seems like everyone is trying to build this functionality on the web. The obvious choice for many are the products of 37Signals (Backpack being the one with the most buzz). Or you can try the oddly named Remember the Milk. Personally, I say you should also add Tasks Pro by King Design onto the list.
Tasks comes in several flavors, ranging from a free script that you can run off of your own server, to a hosted subscription based application. Tasks Pro, the subscription version, offers a bunch of features including recurring tasks, collaboration with others on tasks, email reminders, RSS feeds, and iCalendar subscriptions. The feature set is extensive.
Tasks Pro, and its lesser siblings, are constantly being updated and improved by a devoted developer. It is certainly worth a look.