Source: http://en.wikipedia.org/wiki/Density

Densities of various materials covering a range of values
Materialρ (kg/m3) 
Helium 0.179  
Aerographite 0.2
Metallic microlattice 0.9  
Aerogel 1.0  
Air 1.2  
Tungsten hexafluoride 12.4  
Liquid hydrogen 70  
Styrofoam 75
Cork 240
Lithium 535  
Wood 700
Potassium 860  
Sodium 970  
Ice 916.7  
Water (fresh) 1,000  
Water (salt) 1,030  
Plastics 1,175  
Tetrachloroethene 1,622  
Magnesium 1,740  
Beryllium 1,850  
Glycerol 1,261  
Concrete 2,000  
Silicon 2,330  
Aluminium 2,700  
Diiodomethane 3,325  
Diamond 3,500  
Titanium 4,540  
Selenium 4,800  
Vanadium 6,100  
Antimony 6,690  
Zinc 7,000  
Chromium 7,200  
Tin 7,310  
Manganese 7,325  
Iron 7,870  
Niobium 8,570  
Brass 8,600  
Cadmium 8,650  
Cobalt 8,900  
Nickel 8,900  
Copper 8,940  
Bismuth 9,750  
Molybdenum 10,220  
Silver 10,500  
Lead 11,340  
Thorium 11,700  
Rhodium 12,410  
Mercury 13,546  
Tantalum 16,600  
Uranium 18,800  
Tungsten 19,300  
Gold 19,320  
Plutonium 19,840  
Platinum 21,450  
Iridium 22,420  
Osmium 22,570