EFTPS OnLine
Allows users to sign on and pay their taxes online. An official United States Government system.
www.eftps.gov
IRS: Electronic Federal Tax Payment System (EFTPS)
Tax payment system offered free from the U.S. Department of Treasury. Allows taxpayers to pay federal taxes electronically online or by phone 24/7.
www.irs.gov/efile/article/0,,id=98005,00.html