Skrbl is a delightfully simple whiteboarding tool that lets you draw, type notes, and share files without a software download. Admittedly, my use for and experience with whiteboard products is limited, but Skrbl really impressed me with how quickly I was able to begin a whiteboard and share it with others.
Skrbl also allows you to host files and secure your session with attendees, as long as you register. What's nice is that any unregistered attendee can download your shared files; Skrbl only requires registration to upload. However, one thing to note is the limit on uploading, which is capped at 2MB per file and 10MB of storage. This is too low to share high-resolution digital photos or video files; you're likely better off using a dedicated app like Tubes for such a task. But if you're using the service for business and passing documents back and forth, it will be fine.
See also ImaginationCubed.