Administration Manager Koby Maxwell shares a quick keystroke combination that will cycle through your open AutoCAD files.

"My favorite classic tip for AutoCAD has to be using Ctrl +Tab to quickly flick through all your open drawings. Simply use Ctrl + Tab to go to the next drawing, keeping in mind you cannot be using another command at the same time (such as typing text or drawing a polyline)."
 
Notes from Cadalyst Tip Patrol: This a great time-saving keystroke combination. Pressing the Ctrl and Tab keys simultaneously will let you cycle through your open files. This is a Microsoft Windows function though, not an AutoCAD function. That means it will work in most programs running in Windows. Pressing Shift + Ctrl + Tab will also cycle you through open files, but in the opposite order.