Many spreadsheet applications nowadays have functionality above and beyond the traditional, offering a variety of charts, look-up tables, databases and more functionality than can be mentioned here.
You might be providing an extremely valuable service to many, many people. Your spreadsheet might free up peoples time from boring and tedious administrative work to spend more time doing things they love. It might help keep businesses above water or help them reach for new heights. Your spreadsheet might even help to create jobs or at least keep people employed.
When your spreadsheet start to hit its limits, what options are open to you? Perhaps the best option is to consider the conversion of your spreadsheet to a database solution. Relational databases became viable not too long after the spreadsheet was well-entrenched as the affordable and quick means of gathering data and performing calculations.
You'll need to develop good marketing material. Things like demo videos, which you can find plenty examples on YouTube, screenshots, and keyword rich descriptive text help people find your spreadsheet and communicate the value that sets yours a level above the rest. Excelville.com actually allows you to upload your spreadsheet with all of this marketing material in an easily searchable and user friendly website.