A while ago I attended a Wireshark webinar from Riverbed in which they presented the tool, some beginner and intermediate users troubleshooting scenarios and some lab kit.
Now I got an e-mail that they made it available for download at http://www.riverbed.com/wireshark-virtual-tour
Part of this Lab Kit were available in the Virtual World Tour 2014 webinar on Troubleshooting with Wireshark, held by Laura Chappell and Gerald Combs.
Kit is a free collection of Wireshark training, trace files and tips and tricks for troubleshooting your network. This lab kit contains the following:
If you are interested in troubleshooting with Wireshark, I think this would be a nice place to start. The presentation page of Wireshark Virtual Tour looks a little bit like comics marketing style, but the materials are pretty good.