Coursera is a great site to help teachers learn professionally.  Coursera is FREE and easy to join millions of educators learning new skills daily.  There are over 300 courses to learn from but I found a section for teachers.  The Teacher Professional Development section will give you a great selection of courses that will keep you engaged and learning throughout the summer months. Coursera has many courses on the common core state standards, STEM, and even first year teaching.  Most courses are 4 to 5 weeks long and start soon!  The video embedded below is an overview about Coursera.