As this article rightly points out, business owners need to take as much time planning their retirement as they do operating their business.

"...most self-employed individuals don't take time to learn about their retirement options, even though they may know exactly how they want their businesses to grow. The good news is that you can set up and - in most instances - control your own tax-advantaged retirement program and put aside more each year than the average wage earner." Via Ask the Advisor

This article spells out four specific investment strategies including:

• SEPs - Simplified Employee Pensions
• Keogh
• Solo 401(k)
• Roth and Spousal IRAs

I also like the question asked at the end of the article, "What to do if your business grows?"