Backpack, which is a "personal and small business information manager", has almost immediately made itself impossible to live without. I signed up for an account last night, and I've already used it to organize an entire project.

If you don't already know, Backpack is ... well ... a to-do list on steroids. You create a page and give it a name (usually a small project you need to take on, such as "Build a shelf"). Then you add a description of the project, write notes that include links, photos, or whatever else you want, upload some files so you have quick acces to them wherever you might be, and create a to-do list, complete with checkboxes to indicate completion. You can do all this in just a few minutes, and once you've done it, you've got everything you need to manage a small project in one place. No more keeping track of browser bookmarks in conjunction with directories of files and images. Stick 'em all in one place: on the Web.

Far above and beyond the usefulness of the application, though, is the fact that this thing is slick. All the editing you do to a page is done within the page. It's a WYSIWYG editor. A living web page that does nothing but serve your needs. You mouse-over the title of the page and an Edit link appears. You click Edit and the title is promptly replaced with an editable text box. You enter the new name and click Save Changes. The text box is replaced with the new title. Everything else on the page works the same way, so you can spend your time being productive instead of waiting for pages to refresh and wondering if your session is going to be interrupted with some cryptic developer-speak error message, forcing you to start over.

You can also set reminders in your Backpack. When a reminder goes off, you're sent an email and a SMS message to whatever email address and cell phone number you provide. And if that's not enough, each page you create comes with its own email address, so you can email notes, photos, and images, and they'll automatically be added to your Backpack page. And if you're a Mac user (like me), you can subscribe to your page and see your reminders and such show up in iCal.

This is by far the best web application I've ever used. The user-experience is ... well ... shocking. It makes you wonder why ALL web applications aren't this good. After all, if it's possible to build such great things online, why doesn't everyone build them?

OK, so there's one little catch. The free version (yes, there is a free version) is limited to five pages, 10 active reminders, and comes with no storage space, so you can't store files and images (one of the best features). But for only $5 per month, a very reasonable price for such a great service, you get 20 pages, 40MB of storage, 100 reminders, tech support, and an ad-free experience. Want more? $9 a month will get you a lot more, and $19 a month will get you a ton.

If you're skeptical, use the free version for a few days. Manage one small project with it. You'll see how great it is.

Major kudos go to 37signals, who believed the Web could be used for great things, and then made it happen.