MS Project has been, and remains to be, the most well-used project management software - although probably not the most popular. It's popular because it is intuitive for Microsoft users. It integrates well with Outlook and the other Office Suite products. And it is a commonly used tool, so it is easy to find other users and good local training help and support.
One of the problems to watch out for is that when resource leveling, the software will reassign work and change the schedule. And there is no undo for this act.
The current individual license price is about $450. The version on the market right now is Project 2010, but Project 2007 is still very commonly used.
For MS Project training, we recommend Cindy Prindle, who instructs through Hawkins, Ash, and Baptie in La Crosse, Wisconsin.