Backpack adds calendar and voice notes

37Signals, the poster child of consumer facing software as a service, is making another move that’s sure to please their customers and demonstrate again the advantages of hosted services over desktop-bound software. The popular personal productivity tool Backpack is now offering an online calendar with all paid Backpack plans. The the calendar page was just linked to the Upgrade page and blogger Rex Hamock, the author of the recent MyBusiness article about 37Signals founder Jason Fried, wrote tonight that the calendar feature is on its way.

The Backpack calendar looks a lot like Google Calendar (our review) and includes iCal synching and natural language input but SMS alerts as well.

Just days ago 37Signals officially embraced outside developers CellTell and their service that sends phone messages to your Backpack account.

When we wrote a few weeks ago about ActiveCollab, a free and open source competitor to 37Signals’ flagship enterprise offering Basecamp, debate was fierce over hosted software as a service vs. software downloads to be placed on your own server. Many people contended that the nominal cost of paying a hosted service for maintenance was more than worth it. [Note: Even ActiveCollab announced yesterday a one-click hosting option with DreamHost.]

Now the addition of one new major feature and one cool supported feature to a 37Signals product is a tangible example of the other primary advantage of software as a service – your system got upgraded and you didn’t even know it was happening. Even the next version of Internet Explorer will be delivered by automatic update, it was announced today.

Whether or not you’re a cynic about user generated content, tagging or ajax – it’s becoming increasingly clear that the web service centric part of the Web 2.0 equation is a keeper.