A report from the of the Secretary-General to Economic and Social Council lists the number of executions by country during 1999-2003 (5 leading countries in bold). While the report states that the number of executions are on the decline, you'll notice that the U.S. is still in the top five.
Dem. Rep. Congo 350
Saudi Arabia 403+
Viet Nam 128+
Source: Death Penalty Information Center at http://www.deathpenaltyinfo.org, citing (Capital punishment and implementation of the safeguards guaranteeing protection of the rights of those facing the death penalty, Report of the Secretary-General to Economic and Social Council, E/2005/3, Session July 29, 2005).