Visio 2010 includes software and database diagrams out of the box with the Professional and Premium editions but if you’re using the standard edition, good luck. Once again I’m a little late to the party on this but I wanted to share a collection of UML stencils and a template I ran across today.
I’m far from a UML expert but from what I can tell, this is a pretty complete package that includes tooltips, multiple connection points, and expandable compartments.
If this is something you’ve been looking for you can grab it from the link below. The stencils and templates are available for Vision versions all the way back to 4.1. Be sure to check out the tips and tricks page for descriptions of the more advanced features of this set.