For science this year, the boys (grades 7 and 8) and I used the free lesson plans from The American Chemical Society available at http://www.middleschoolchemistry.com/
Designed for use in a traditional classroom, these lessons were easily adaptable to a homeschool environment. Topics covered include: matter, changes of state, density, periodic table & bonding, water molecule and dissolving, and chemical changes.
This was an incredibly hands-on program which the boys really enjoyed. A few supplies are necessary to buy or borrow, but overall the cost was small for such a quality program. The handful of times I didn't have the materials at my disposal, we simply read through the lessons and watched the accompanying videos. A test bank of questions is also provided so that one can create tests for each chapter with ease.
I highly recommend this program for anyone searching for a chemistry program designed for middle-schoolers.