Having used software source code control systems for almost 20 years, it seems unreasonable to not maintain software in a system like CVS (I have not made the move to Subversion yet).

Recently, I made a fairly obvious extension to my own work flow process by creating additional CVS repositories for customer work logs, design artifacts, etc. In addition to obvious benefits of versioning, etc., I also like the ability to sit down at any computer anywhere and securely have access to all of my work materials.