I am a big fan of Remember The Milk and the article rated RTM the winner in the to-do list category.
Winner: RememberTheMilk reinvents the to-do list in a snazzy interface that lets you make lists in configurable categories, all laid out on the front page as tabs. Adding to-dos is easy, though adding deadlines, notes, and time estimates is unintuitive.I take a little umbrage (if you can only take some) that they gave Gmail runner up status.
You can add to-dos using natural language such as "Call Ted next Thursday," sync with your calendar via the widely supported iCalendar format, and set tasks such as "Pay credit card bill" to recur. RememberTheMilk sends reminders through instant message, e-mail, text message, or a combination of these. You can also upload tasks via a special e-mail address that the site gives you.
It's a tremendously well-rounded free product, with neither more nor less than you need to get and stay organized.
But its limitations--the inability to add new folders, to open multiple messages in one window, to filter e-mail, and to right-click on anything--will surely frustrate power users.They fail to mention tags - that which power users will love the most. I've been thinking of totally dorking out and writing a post about the obvious superiority of tags in organization. But I'll save you from that for now.
In terms of the next, new interesting application, I'm going to check out Meebo, a web based, multi protocol IM client. I've been using IM more and more for work now that I am a remote worker and one of my large projects involves a team spread across the country, both in-house and consultants. I'll let you know what I think.
The article is a long read, but I recommend it. Check it out.