if you used the search you would find that the usb infinity pheonix is by far the most popular choice. dont get this confused with usb infinity unlimited.
Well It depends on your PC a little I would say if your PC as a serial Port then for me it would be The Infinity Usb Phoenix or the Dynamite, But if you have a PC with no serial port then the Infinity Usb unlimited (I must admit I've not had the best of luck with the unlimited) I find it a bit hit & Miss.