Good Net Resource for Identifying Wood?

I'm curious about identifying the wood used in the floors of my house.
It's an older house (100+ years)with finished wood floors, which appear
to be the original subfloors. I'm pretty sure the floor is pine (no
experience with flooring, but I'm fairly good at ID'ing wood used in
furniture), but I hear people talking about "yellow pine" and "heart
pine" and so on, and I've grown curious about what kind of pine this
is. Does anyone know of any good Internet resources for looking at and
learning about different kinds of wood? (I don't object to buying a
book, per se, but since this is just kind of a passing curiosity....)
Or perhaps one of you "wood pros" can provide a description of the
identifying characteristics of one kind of pine vs. another?

Don't have direct link to web site, but the US Forest Service web site
is a veritble plethora of useful information. :)

Where's the house located? At that age, particularly if in northeast,
likely to be one of the "white" pines.

Characteristics of yellow pine is (naturally) a yellowish hue and being
harder and having a more pronounced grain. Most yellow pine flooring
was also narrower strip flooring as compared to most white. If it is
stained and finished, may not be particularly easy to tell. One
characteristic of an old white pine floor would be quite a bit of wear
and dents and dings as it is pretty soft. That's kinda' subjective,
though, as the wear and abuse it got over the years could be far
different in one case than another, of course.

Posting a picture somewhere would be good...

Jo Ann