Your company is a massive jigsaw puzzle and each employee is a unique piece. Once a week go to a different department and ask someone to show you what they do. If they use software you’ve written, find out how they use it. If not, find out how they fit into the big picture of your organization.
The more you know about your co-workers, the more you’ll understand the puzzle. The more you understand the puzzle, the more indispensable you become.