My seventh-grade daughter has a tee shirt that says "Pre-Algebra: the beginning of the end!" And if high-school math is the end objective, then pre-algebra certainly is the beginning. Here are my picks for sites that both explain pre-algebra, and provide an opportunity for practice.
Textbook publisher Glencoe has created five WebQuests that can be enjoyed by all pre-algebra students, even those using a different pre-algebra text. Each Internet project includes a task that requires online research, and suggested websites are included. For example, Unit 1 involves creating a website or a brochure promoting three seven-day vacation packages for a family of four. Each package must include transportation, lodging and entertainment, and cost between $2500 to $5500.
Just like a textbook, the pre-algebra section of Math.com is divided into chapters that explain concepts, include lots of examples, and conclude with a quiz. The only difference is that the quiz is interactive and self-scoring. Chapters are Numbers, Ratios, Factoring and Fractions. For fun with puzzles, jump over to the Games section (you'll find it on the horizontal menu.) Other notable clicks are the math glossary, and the specialized calculators (such as percent and square root) found in Calculators & Tools.
Looking for something special for extra credit? Click on over to Math Forum for the Pre-Algebra Problem of the Week. When you've got it licked, you can submit your answer online by choosing your school from the state list. If your school isn't listed yet, go ahead and add it. As you submit your answer, you'll have the option of asking for free (or paid) mentoring, And finally, you'll be able to check your answer (i.e. see the solution.)