Web workers and small teams are always on the lookout for really solid, affordable productivity apps, especially when it comes to task management.

Although the field may already seem crowded with popular products like Remember the Milk, Things and Producteev, there's one more that's worth checking out, called Flow.

Flow is a new task management Web app that comes from MetaLab, a design firm that specializes in very slick, app-like interfaces for Websites, desktop and mobile applications. Accordingly, Flow is particularly well-designed, with a clean interface and the feel of a desktop app.

In terms of features, it offers the usual: entering and managing tasks, deadlines, tags, and the ability to enter new tasks via email.

What's a little different about Flow, at least compared to something like Remember the Milk, is that it can be used collaboratively, as well as on an individual basis. Team members can be added and tasks can be delegated to them. Rather than a static list of to-do items, each task can be commented on by team members.

In Flow, task lists can be broken down by "project," but that's about as far as things go in the direction of project management. Flow isn't trying to be a substitute for more robust productivity suites like Basecamp and Highrise, but by the time it comes out of beta, it may give other task managers like Things and Remember the Milk a run for their money.

One common shortcoming in some of these to-do list managers is cross-platform compatibility. For those of us who work off of several devices each day, a Web-based desktop solution is not enough. We need native or Web apps for iPhone, Android, iPad and Blackberry for these tools to truly be useful. Remember the Milk, for example, has iPhone, Android and Blackberry versions, but its iPad app is still under development. Meanwhile, Things is really impressive, but it's only available for Mac and iOS and it's not cheap.

So far, Flow is only available as a Web app, but they're working on an iPhone version, which is "almost done" according to a recent tweet from MetaLab.

Flow is currently in private beta, but you can sign up for an invite here.