Aside from the ubiquitous Word and WordPerfect, or the equally omnipresent Outlook and kindred email programs, my candidate for the software that in-house lawyers use most intimately and frequently is the law department’s shared drive.
Everyone can access it. Everyone can create a directory sub-structure on it that makes sense to them, and everyone can rummage around in it to find material that might help them. A shared director is the poor man’s knowledge management system.