OK, I put my hand up, I should have done this site a LONG time ago, anyway Dollars2Dollars.com is now live, at this time it's fixed to US Dollars against one other currency from Canadian Dollars (CAD), Australian Dollar (AUD), New Zealand Dollars (NZD) or Hong Kong Dollar (HKD).
It's the same usual easy format, a nice simple calculator and some history charts.
Exchange rates are updated hourly at present.
I'm going to work on the UI to support more conversion options (i.e. Australian Dollars to New Zealand Dollars).