According to the Cellular Telecommunications Industry Association, specific absorption rate (or SAR) is "a way of measuring the quantity of radiofrequency energy that is absorbed by the body." For a phone to pass FCC certification, that phone's maximum SAR level must be less than 1.6W/kg . In Europe, the level is capped at 2W/kg while Canada allows a maximum of 1.6W/kg.
CNet has a list of the radiation level of different phones, ordered by manufacturer. My Nokia N80 has a SAR value of 0.86, which leaves it around the middle average. Best (minimum) SAR values of current phones are around 0.16 W/kg.