I suggest your check out Comindware and try their 30-day fully-functional trial of their new workflow automation software. It's free and it supports an unlimited number of users, tasks and subtasks. The graphical Workflow Builder enables visual drag-&-drop design and editing of workflow processes — no IT programming or technical expertise required. Go to http://www.comindware.com to check it out and signup for the free trial. Your feedback to them is welcomed on the site.