It's called WordPress.
WordPress is a free and open source blogging tool. Geeks often refer to it as a “dynamic content management system (CMS) based on PHP and MySQL”.
You don't need to worry about that, but if you need convincing take note that as of May 2012 Wikipedia reckons WordPress is currently the most popular CMS in use on the Internet.
So What's This Got to Do with You?
It's ideal for your bootstrapped micro-business or small business because it's solid, reliable and free.
To get the most out of WordPress you need a custom theme that positions your brand and communicates with your target audience. If you don't have money to invest in a custom design, you might want to check out some awesome turnkey themes that I talk about in this video.
P.S. If you do try a Studiopress theme based on the Genesis framework, let me know. I'm very curious to hear what you think.