Google just announced that Tasks will be the first feature to graduate from Gmail Labs to become a default feature for all Gmail users.

Gmail Labs, which launched about a year ago, holds a collection of experimental additions to Gmail that users can try out by enabling them within their Gmail's settings. It also provides an interesting window into Google's application development philosophy.

Tasks provides a to-do list within Gmail optimized for mobile access and integration with Google Calendar. Senior product manager Keith Coleman says that the decision to add it to the main product was partly based on how many users had signed up to try it and how many have continued to use it. Coleman adds that a handful of other Labs experiments will likely graduate in the near future.

At first, Google wasn't sure if Labs would be a viable way to test features for Gmail, Coleman says, in part due to the technical complications that it introduces. You see, the system generates a different JavaScript codebase for each Gmail user based on which Labs products she has enabled. Since Gmail launched 51 Labs experiments in the past year, there are an astronomical number of possible Gmail builds--far too many to test internally.

But Google considers the experiment a success--so much that the company expanded the system by introducing Google Calendar Labs today. Calendar Labs will offer experimental features such as a time-zone gadget and the ability to track whether friends are free or busy.

Since Google has dropped the famous "beta" tag from many of its applications, Labs gives the company a way to keep the product evolving without disrupting customers who depend on it for business reasons, says Ken Norton, senior product manager for Google Calendar.

While Gmail Labs is known for some quirky widgets, like Mail Goggles (jokingly designed to stop embarrassing late-night e-mails), it also supports efforts to appeal to business customers. Calendar Labs will permit third-party developers to make their own adjustments to Calendar, allowing businesses to make necessary customizations, Norton says. This feature is only designed for use within a particular company: there's no way to make these outside features publicly available. A similar trick is possible in Gmail Labs, Coleman says.