Planscope is described as 'Agile project management tool for freelancers and small teams' and is an website in the Development category. There are three alternatives to Planscope, not only websites but also apps for Self-Hosted solutions, iPad, iPhone and Kirby. The best alternative is Pivotal Tracker. It's not free, so if you're looking for a free alternative, you could try Trajectory.
Tracker is a story-based project planning tool from Pivotal Labs that allows teams to collaborate and react to real-world changes instantly. Its based on agile software methods, but can be used on a wide range of projects.