Several of Projector's features I really like are the ability to share a project plan by publishing it to a web page and the ability to attach documents to any task in the project plan. The latter feature can be very useful by allowing project teams to attach deliverables (i.e., requirements documentation) to the plan once they are completed, or by letting project managers attach detailed descriptions of tasks for the team. There's also an "Export project to my MobileMe account" command, although it currently sends an image of the page to the .Mac HomePage folder -- an old feature that won't be around much longer.
There are three primary views available to Projector users -- a resource view, which shows the task timeline for every resource working on the project; a Gantt chart view, showing the relationship of tasks over time; and a report view, which can shows progress and costs either through analyzing each task in the Work Breakdown Structure or by resource. Each of these views can be exported to a web server.
Each To-Do item can be added to an iCal calendar, making it simple to see tasks with a glance even when you're out of Projector. I'd frankly like to see a companion iPhone app, since it would be wonderful to track time and mark task completion even when I'm not near a Mac.
Competitive Mac or web-based PM applications include SharedPlan, @task, OmniPlan, Merlin, and FastTrack Schedule 9. If your organization leans towards Microsoft Project, you can even consider running that Windows application in a virtual machine on your Mac.
There's a free demo available from App4Mac that is limited to 20 tasks or processes. Check out the gallery below for pictures of Projector in action.