According to Alexa these are the top 10 most visited project management software websites…

1.  Top 10 Project Management Software Websites WikiPedia
Explanation of the term “project management software” on Wikipedia.
http://en.wikipedia.org/wiki/Project_management_software
2. www.basecamphq Top 10 Project Management Software Websites BaseCampHQ.com
Basecamp PM Software website. Commercial.
http://www.basecamphq.com
3. www.aceproject Top 10 Project Management Software Websites AceProject.com
Ace Project PM Software website. Commercial.
http://www.aceproject.com
4. www.attask Top 10 Project Management Software Websites ATTask.com
AT Task PM Software website. Commercial.
http://www.attask.com
5. www.axosoft Top 10 Project Management Software Websites AxoSoft.com
AxoSoft PM Software website. Although emphasis on bug-tracking. Commercial.
http://www.axosoft.com
6. www.celoxis Top 10 Project Management Software Websites Celoxis.com
Celoxis PM Software website. Commercial.
http://www.celoxis.com
7. www.easyprojects Top 10 Project Management Software Websites EasyProjects.net
EasyProjects PM Software website. Commercial.
http://www.easyprojects.net
8. www.projectinsight Top 10 Project Management Software Websites ProjectInsight.net
ProjectInsight PM software website. Commercial.
http://www.projectinsight.net
9.  Top 10 Project Management Software Websites MinuteMan Systems
MinuteMan PM desktop software. Commercial.
http://www.minuteman-systems.com/
10. www.project management software Top 10 Project Management Software Websites ProjectManagementSoftware.org
Overview site of PM software.
http://www.project-management-software.org