Some of these are blogs, such as the Gray's Anatomy page. These can be very helpful as you are trying to get accustomed to this field of study and want to learn more from people who are already working as phlebotomists. Other sites, such as the Unofficial Phlebotomy Page, are more of a general guide about the body and the systems that carry blood. This sort of thing is good when you're looking for a quick reference for a school paper. Some of the sites are also geared towards professionals working in the field and feature articles about the latest news in the field. And then there are sites that offer healthcare job information, so you can look for open phlebotomy positions to apply for.
As you enter the field of phlebotomy and make your way through your career path, you will probably find a number of sites on your own that you begin to rely on for information that is relevant to you. This collection of websites and blogs is a good place to start.