Q: developing online course is a project. Do you know any free project management tools available online?

A: this article gives you a list to choose from: http://www.smashingapps.com/2010/02/15/10-free-tools-for-effective-project-management.html
The additional links are in the comments below:
http://www.oneplacehome.com/
https://launch.unifiedinbox.com/
http://openatrium.com/
http://www.gtdagenda.com/
http://www.teamworkpm.net/

etc.

Q: What Should Students Learn in the 21st Century?

A: I just heard Charles Fadel's talk at the Learning &the brain conference. You'll find an answer here: https://vimeo.com/50409698
Charles Fadel shares his findings from across many disciplines and groups about what students should learn in order to be prepared for the 21st century. He discusses the exponential growth of technological capabilities, the continued automation of traditional tasks and professions as well as the impact of technological innovation. Looking at the race between technology and education, he urges teachers to consider how best to provide students with higher order skills in order to prepare them for success in the communities and workplaces they will participate in.

Q: Is it important to reflect United Nations Millennium Development goals in objectives for my course?

A: By adopting United Nations Millennium Development goals in your curriculum you support the universal primary education. Here is the link to 8 goals and other resources: http://www.un.org/millenniumgoals/

You can learn more about initiatives, especially about sustainability: http://www.un.org/millenniumgoals/environ.shtml . For example,  use fact sheets to explain to your students where  do we stand regarding drinking water situation  etc.