By now you're likely out of school and about to hit the beach (or some other vacation place for a little R&R)...hopefully! School is probably the last thing you want to think about during your summer vacation, but reading wouldn't be so bad, would it? Grab a copy of Danica McKellar's Math Doesn't Suck and read a chapter a night.
If you're 30+ you most likely will remember Danica as Wendy on The Wonder Years. She went on to graduate with a degree in Mathematics from UCLA and write three bestselling books. Math Doesn't Suck is really geared towards middle school girls but it actually has some interesting ways to think about (and therefore teach) math topics. My personal favorite is the "birthday cake" method for finding GCF/LCM! I typically recommend this book to students entering Pre-Algebra.
Here's a list of Danica's books in case you want to do a little more reading:
1) Math Doesn't Suck - geared towards ages 9-12
2) Kiss My Math - for Pre-Algebra students aged 11-13
3) Hot X: Algebra Exposed - for ages 13-15+
4) Girls Get Curves: Geometry Takes Shape - set for release in August 2012!