Alder: full and rich, with fat low-end, nice cutting mids, and good overall warmth and sustain. Alder is generally considered to be one of the "traditional" Stratocaster body woods.
Ash: exhibits a "snappier" tone with a bright edge, but with a warm bass and long sustain. It is often considered as the other "traditional" Stratocaster body wood.
Poplar: one of the softer hardwoods, nicely resonant with a meaty tone. Many guitar manufacturers as a substitute for alder are using this wood, as it is quite similar in tone.
Basswood: the principal wood used on many Japanese made instruments. This is due both to its tonal response, (once again, very similar to Alder) as well as the fact that Basswood is much more readily available to the manufacturers in Asia.
Mahogany: deep warm mids, good sustain and nice "bite"
Maple: punchy, bright, and has a nice bite on the high end. Often used only as a laminated top instead of an entire body, as it tends to be a particularly heavy wood.