Redmine

That would add too much to user interface. A project selector is good because they are a core section of Redmine (i.e. almost everything is done on projects) but I'm not sure that one for users would be worth the space. Maybe there can be a different page to show the users and to get to their account pages?

I think a separate page would be great. Maybe a permission is needed. I don´t want that different customers can look at each others profile...

I think the way there is a 'Project page' link on the top menu, there should be 'Users' link on the top menu.

Currently there is no way for non-admin to see list of people; they can only see individual profiles.