On the main Issues page, you can click Everyone's Issues, or Assigned to me.
If you want to view the tasks assigned to a particular person, you can click the search icon, and on the left choose the assigned to anyone drop-down, then choose from a list of assignees.
But how to I list all the items which are not assigned to anyone?
nowyou could dono:assigneeon the filters – Aivan Monceller May 18 '15 at 16:10