Redmine

Committed in r817.

You can bulk edit issues by clicking on the edit link (little
pen icon) at the upper-left corner of the issue list.
Most properties can be set (priority, assignee, category, fixed
version, start and due dates, done ratio) and a note can
be entered.
Only issues of the current project can be selected for bulk edit
(subproject issues can't).

Since this never got closed ;-) and it's a minor suggestion I'll add this here - allow custom field values to be batch edited along with the standard ones.

A small note: the small pen icon has been actualized to a contextual menu that appears by clicking with the right mouse button.
So first select the issue by clicking on the check boxes on the left and then right click! Magic! ;)

Just wanted to add: AWESOME MAGIC!

Indeed, I found very nice to have this hidden menu, like, you generally do not expect a web page to support right clicks. So normal users wont use this, so they do not destroy your data so easily!