Ethereal has a rich set of display filters (33,129 as of version 0.10.13) that let you quickly drill down to the traffic that you want to see. Below you will find a list of all of the protocols that Ethereal supports. On each protocol page you will find a list of supported display filters for that protocol, along with data type and version information.
Information using Ethereal's display filters can be found in the ethereal-filter(4) man page or in the User's Guide