Main recommendations:
- EPGY Open Enrollment (Math K-7 only; it is now called giftedandtalented.com and has gone up in price; see other threads about this on this forum)
- Art of Problem Solving Prealgebra textbook + solution manual ($60 total)
- Art of Problem Solving online Alcumus (free).
One unorthodox suggestion:
- Great Source 'Math to Know', ... ,'Algebra', 'Geometry' (6 books).
These are not textbooks, but kind of encyclopedia/reference books.
The first 4 are similar, but vary in the level.
These are great for 'telescoping' far ahead.
(To get the feel, use a library, or buy a used copy.)
A lot of people like UK's Mathematics Enhancement Programme (MEP):
http://www.cimt.plymouth.ac.uk/projects/mep/ (online, free). (I have not personally used this but it looks good. See well trained mind accelerated learner forum.)
