For current information on constants, dimensions and units, visit <http://physics.nist.gov/cuu/index.html>.
Many introductory physics classes do not treat continuum mechanics. An excellent site that introduces continuum mechanics very clearly and integrates it with the material that is taught in most introductory physics classes is at <http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html>. The fluids branch is at <http://hyperphysics.phy-astr.gsu.edu/hbase/fluid.html>.
Another useful site that is (intentionally) more limited to introdutory material is <http://www.physics.uoguelph.ca/biophysics/>. The material on Archimedes' principle is misplaced and should be under fluid statics.