One quick way to start would be to buy (or get from the library) a book titled "Identifying Wood" by R. Bruce Hoadley. It's published by Taunton Press. It covers many species and is a great reference.

The book includes sources for wood identification both free and for a fee. The free service will identify up to five samples if there is a "clear need for wood identification". It's the:

Center for Wood Anatomy Research
U.S. Forest Products Laboratory
1 Gifford Pinchot Drive
Madison, WI 53705-2398

Hoadley's book explains proper sampling techniques. It's relatively non-destructive, meaning small samples of each species in question.

Good luck with your research.