Human Resource Management
I deal with human resource management on a daily basis. It's part of my day job. It's kind of neat, really, to be the guy in the company that everyone else goes to to get information about their hours, how overtime works, their benefits and how to manage them, and stuff like "how do I reduce all these garnishments on my wages?" Keeping track of employees and their dependents, and all the various details that go with them (how many dependents exactly, and whether they are natural children, adopted, or step-children) is a bit tricky, so I've developed a human resource management service at I had already built many of the pieces of this puzzle during the course of my duties, so putting it all together hasn't been as hard as it would have been if I were starting from scratch. Still, there are lots of interactions to consider as I build out the features and I'm sure I'm in for one of my famous "learning experiences". 

Besides employee tracking, I've included an online time clock feature, an employee manual wizard, and an evaluation (appraisal) service. It's always nice to build a service to solve your own problems. Who better to do so, eh?