What is the best extensible project management software for desktop?

The best project management software that is easily extensible is Planner Developer by P2ware Ltd. (www.p2ware.com). Planner Developer: * is a PMO (Project Management Office) software version * allows for creating PM own templates * allows for adding new properties to already existing objects * allows for adding new formulas computed from existing values (e.g. calculation of specific values, new risk model, etc.) * also allows for creating perspectives, filters, etc. Planner Developer can be used by PMO in large organisations as well as individual project managers. Using Planner Developer one can easily tailor his/her project management templates to actual needs.