Thats true about resting up till school starts but most are type As and can't wait before school starts and I know you will not just sit by till school starts so...
Go buy yourself the book Clinical Anesthesia by Morgan and Mikhail and start reading. Pay attention to the early chapters, like drugs, gases and the basics. This ought to get you started!!
The other things you could do is start reviewing your anatomy. Especially the stuctures in the larynx, neck, etc... If you still want to do more, read up on your lung, liver, kidney, cardiac physiology.
That should keep you busy over the summer.