My DS will be going to a school that will teach him algebra/geometry formally next year. They recommended Algebra: Structure and Method (Brown, author). I found it on half.com for a few dollars for anyone who's interested. It's the basic algebra textbook used in a lot of schools.

I've been happy with it (bought it two or three months ago).

I also made heavy investments in graph paper for DS for graphing. This seems to be one of his favorite algebra-related activities (presumably because it combines art and math). I've had fun writing series' of progressively outlandish equations for him to graph. Some require taping sheets of graph paper together and the results can be wide parabolas or goofy curves.

Val