Hi Dan; I think there are a number of sites out there already with what you recommended. This is but one example: http://www.asavari.org/ragindex.html Saw this list before. This is only a small sample of the ragas that are out there....
I think the ragas listed on the left scroll on that page are mostly, if not all Hindustani. I'm sure others can do a much better job than me in definitions, but I'll give it a shot.
Carnatic (or Karnatic)is simply the type of music indigenous to south India as opposed to the Hindustani north. Its largely an original and pure form in contrast to the more outside-influenced form of the north.
Thaat (is spelled several ways) is essentially a scale like major, minor, etc. The equivalent Carnatic term is mela. There are 10 Hindustanti thaats and 72 Carnatic melas. Each thaat or mela has a characteristic ascending and descending scale, and has a major raga in the scale associated with it (for example, the Kalyan thaat has Raga Kalyan as the primary example).
Two books for newcomers (and those who have been wallowing in it for a while) are:
1) Music In India, the classical traditions by Bonnie Wade. Wonderful intro to both north south musical traditions, genres, instruments, theory, practice, etc. Only negative is there is no audio supplement. Am considering working on linking audio clips/more photos, listening list, etc. to complement the book.
2) Raganidhi (3 volumes) by Subba Rao. This is one of the most comprehensive books on the know raagas (north and south), matching, etc. The asavari web site is quite inaccurate...Subba Rao's book is much better. However, Wade (or some of the information in it) is needed to appreciate this book.