Free Wireshark Core Training
Free Wireshark Core Training WCT01 Network Analysis Overview and WCT02 Introduction to Wireshark. These videos are taught by Laura Chappell. Both courses total a little of 4 hours of lectures, demos, and examples.I'm only though about half of the material so far and it is really good and will be a good resource for the WCNA exam.
The videos can be viewed on YouTube