The Natural Sciences CLEP test is a great CLEP test. Most schools will give you six college credits for passing it. This test covers Biology, Chemistry, Physics and some Earth Sciences.
Included is information in the following areas:
Thermodynamics
The Universe
The Origin of Life and Evolution
The Earth
Surface Features and Geological Processes
States of Matter
Stars
Sound
Solar Systems
Relativity
Population Biology: the Struggle for Existence
Organism Development
Magnetism
Light
Hydrosphere
Geological History of the Earth
Genetics and Patterns of Heredity
Genetics and Bioenergetics and Biosynthesis
Galaxies
Elements, Compounds, Reactions, and Atomic Bonds
Electricity
Earth's Structure
Earth's Atmosphere
Classical Mechanics
Chemical/Physical Sciences
Cell Structure and Division
Biological Sciences
Atomic & Nuclear Structure