Learning the The History of Visual Communication is something every designer should do. If you are going to or have gone to school for design you will probably become well versed on this topic, but if you want to brush up on your design history right now you should check out this website because it gives you a quick overview of the The History of Visual Communication.
They basically go over everything from the very first writings and drawings on rocks and caves all the way up to modern day computer graphics. They touch on many important movements and show examples from many famous designers and design schools.
If you an art history or design teacher then you will really love this site because it comes equipped with high res slides which you can easily download and show to your students.
The History of Visual Communication