One of the best overall websites that I have found that gives moms a wealth of information regarding the different aspects of pregnancy is the following link:
http://www.parents.com/parents/category.jsp?catref=AB2
On the Parents website, you can sign up to receive free weekly updates on the growth and development of your unborn baby. Even if you are not expecting yet, you can still receive weekly updates on how to prepare for pregnancy. Some other benefits to this website is the information regarding the different trimesters, baby naming, conception, labor and delivery, post partum, fertility options, and adoption.
This website has been a valuable resource to me and I know that it will be to all expectant moms.
Other Sources that I have found to beneficial:
http://health.discovery.com/centers/pregnancy/pregnancy/pregnancy.html
Free pregnancy email newsletter, fetal development, and much more
Your online pregnancy calendar and week by week pregnancy guide
If you are trying to get pregnant, pregnant, or have a family, this website a good resource for pregnancy and baby – spanning preconception, pregnancy, and parenting
A guide for moms-to-be with tips on pregnancy, nutrition, fitness, exercises, baby care, and weight loss.
A pregnancy and trying to conceive resource which includes week by week pregnancy calendar, online birth planner, ultrasound, and labor and delivery.
**Please be advised that some of these websites could contain graphic information.