Although I do not love the titles, this is a great book series written by Danica McKellar. The books relate math to a lot of middle school students' biggest concerns (crushes, shopping, and technology). The websites are also quite helpful for the students on many different topics with forums and sample problems.
Math Doesn't Suck is a book that will walk the students through some of math's toughest fundamentals. This is the first book in the series that addresses skills students learn in sixth and seventh grades. The topics in this book are: factoring, greatest common factor, least common multiple, fractions, exponents, decimals, rates, and proportions.
Kiss My Math is the second book in the series. This book is targeted towards Pre-Algebra. The beginning of the book really focuses on the variables and solving problems with variables. Other topics the book covers are: integers, the poperties of addition and multiplications, absolute value, central tendency, combining like terms, the distributive property, word problems, inequalities, graphing, exponents, and functions.
Again, these books are wonderful for relating the topics students struggle with to everyday knowledge and life. They also have many extras that the students enjoy.