This is the famous "Ask Dr. Math" website, an excellent
place to ask any math
question. Don't expect instant results, however. It may take a
day or two.
However, there's a huge archive of previously asked questions, so
maybe your
question has already been answered.
http://www.mathforum.org/dr.math
The "Princeton Review" writes study manuals for all
kinds of standardized
tests, but they're most famous for their excellent SAT study
guides.
http://www.review.com
A tremendous resource for high level information about polyhedra,
and really
fun interactive stuff. George Hart is also a clever and ingenious
sculptor.
You will love polyhedra after spending some time here. And he
LOVES ZOMETOOLS!
http://www.georgehart.com
This is our Geometry textbook publisher's website. You can watch
tutorial
videos and get homework help, and a lot more.
http://go.hrw.com/gopages/ma/geo_07.html
Here is an amazing games & puzzles site. The URL takes you to a
page in a
large math website called "Cut The Knot".
http://www.cut-the-knot.org/games.shtml
Here's a no-frills, PRE-CALCULUS ONLY website. It has LOTS of
problems with
solutions worked out, and it's organized by topic. It's an
excellent resource!
http://www.math.ucdavis.edu/~marx/precalculus