As of 2006, the most commonly prescribed antidepressive medications in the USA are, ordered greatest first:
Escitalopram (SSRI)
Sertraline (SSRI)
Venlafaxine (SSNaDRI)
Bupropion (SNaDRI)
Duloxetine (SSNaRI)
Paroxetine (SSRI)
Note that Bupropion is not available as an antidepressant in the UK due to prominent side effect problems.