Here is a link to a Key to the Genera of Hypogeous Ascomycetes by Drs. James Trappe & Michael Castellano. At the beginning it also has a key to assist in separating Ascomycetes from Basidiomycetes. You can also download an MS Word version of this key here.
Here is a link to a Key to the Genera of Hypogeous Basidiomycetes by Dr. Steve Miller of the University of Wyoming. You can also download a PDF of this key.
Both of these keys are designed so as not to require a microscope. They both have lots of great information in their introductions, including explanations of what technical terminology is necessarily used. They are only designed to identify a truffle to the genus (group) level. In most cases, positive identification of a truffle to species level requires a microscope, a fair amount of technical expertise, and a lot of practice!
Sometimes the key may ask what color changes are induced by either KOH (a 5% aqueous solution of Potassium Hydroxide) or Melzer's solution (an iodine solution). Neither will be found at your grocery store but they (or their equivalents) can be obtained with some persistence. More information on these chemicals can be found here. The two main iodine reactions are called amyloid and dextrinoid. A bluish to blackish response to a drop of iodine is an amyloid reaction, and a yellowish to reddish-brownish response is a dextrinoid reaction.For the aforementioned reasons, species level keys likely won't be very helpful to most folks. As it would happen, some of the most commonly found truffles (Rhizopogons, for example) are among the most fiendishly difficult to identify to species. That being said, click here to see a key for Rhizopogons or click here to download the same key in MS Word format (600K). This key requires a microscope and the chemicals mentioned above (Melzer's and KOH) - it is not for novices (few truffle keys are!). We'll post more species-level keys in the future - Gymnomyces, Hydnotrya, Leucogaster, and Tuber keys for common PNW species are "in the pipeline."
When and where do PNW truffles fruit? Click here for fruiting and habitat association data for most common Pacific Northwestern truffles. This is the same info included in our new fully illustrated "Field Guide to North American Truffles".
Below is a list of some common genera of truffles in the Pacific Northwest, organized by family group. This list was condensed by NATS from a worldwide compilation by Dr. Michael Castellano.