Here's a utility proc that I had lying around for automatically generating a version of a text that is suitable for usage in a URL. It transforms e.g. "Foo Bar" to "foo-bar". I tried to add some automatic numbering so that it can be passed a list of existing URL's so that it can generate foo-bar-2 if there is already a foo-bar URL present to avoid collisions.
It might be useful to optionally create the URL automatically, so that the admin does not have to insert a short name manually every time when creating a new forum.