I have a few favorites that depend on what you are looking for!
Apologia is wonderful, especially if you want to teach several different levels the same thing AND if you love hands on projects. You focus on one specific subject for the year and your kids get to dig in deep. This one receive rave reviews from many homeschoolers. Purchase it here.
http://www.curriculumexpress.com
If you are looking for more of a general science, where you cover a bit of physical science, life science and earth science all in one year, then there are different options:
For a colorful program that just provides the key information with lots of experiments to make the learning come alive, check out Singapore Science. This one is broken down into five units for the year, each covering a different area of science and is awesome for the visual student. You can view a description and sample pages here
http://www.singaporemath.com/MPH_Science_s/66.htm by clicking on a title and order it for a discount here
http://www.curriculumexpress.com.
For a Christian based program that takes the scientific principles you are learning and applies them to the Bible and Christian living, check out ACE. This one is written from the perspective of a teacher and student interacting, includes a few experiments and is filled with Biblical application. Students receive 12 workbooks for the year--in each they learn a specific character trait and a memory verse. I do not know of any site where you can see the program, but you can purchase this program here
http://www.curriculumexpress.com.
Hope this helps!
Jessica L. Parnell is a homeschool consultant, evaluator, and principal of Bridgeway Homeschool Academy, an international homeschool academy, that has been serving the homeschool community since 1989. Visit jessica-parnell.com my personal blog.