Out of the box Redmine doesn't look like it has a lot of options for managing clients, but you'd be wrong - with a little customizing you can at least fake it. There are two parts to this - set up a new user group and add some custom fields for users.

The first step is to create a new user group called Client:

This past week I moved an install of RedMine from one server to another, or rather I just moved the database over and checked out the SVN code again. After getting it going correctly I promptly forgot about the fact it was at a new location and just worked away on my assigned tasks. Well, as it turns out I'd completely forgotten about the uploaded files, which now wouldn't download anymore.