www.ingdirect.com
If you ignore currencies and only go on the %age, you'll make $US437.50 (5.25%) in a month. This account calculates interest daily and pays monthly, so it compounds. If you leave the account untouched for a year then the effective rate is 5.38%
This account is 'online' which means you transfer funds electronically. No fees so it's a true interest rate.