A custom domain name can really help to give your blog a more professional look, as well as making your blog much easier to remember. For example, http://mysuperblog.blogspot.com can be turned into www.mysuperblog.com.
You can purchase any domain you like, from any website you prefer (so long as it is not already taken). We tend to recommend GoDaddy because their control panel is easy to use and their prices are very competitive. You can pick up a .com domain for $1 on this page. Please note this is an affiliate link ...we earn a few pennies if you purchase there 🙂
After you have purchased your domain, you can then install it on your Blogger account via this guide.