Ask HN: What can a small business do to grow excess cash?

I'm self-employed with a web development business structured as an S-Corp. I maintain a payroll where I pay myself, and contribute towards a retirement savings account, but my business tends to have excess cash that sits in savings. At this stage, I'm not looking to increase headcount. Is there anything better I could be doing to grow this cash apart from increasing my own payroll and investing it in my personal investment accounts?