A great way to get started with Bootstrap--or to expand your repertoire--is to check out the free and affordable themes and templates for Bootstrap that are available on Bootstraphunter.com. This site is a digital marketplace for responsive HTML website themes and Bootstrap templates. The idea of the site is to provide a one-stop shop for your development needs.
There are some free themes you can download, but the premium themes are priced very competitively with some available for just $5. These are nice-looking themes, and some are geared toward specific types of businesses such as real estate.
If you're a web developer, you can partner with Bootstraphunter.com and make your themes and templates available for sale on their site. When you license your work with the site, you receive royalties when your work sells.
There are already some great designs available on the site, and the site only launched a few days ago. I'm sure the site will grow very quickly as word gets out.