Just got a new product…the Entrance MicPort Pro. The cool aspect of this is that it takes a high end XLR input mic and makes it into a USB mic. It works in Windows and Mac , and I can confirm that it works in Mac OS 10.5 (Leopard). I will caution that this was with my setup only, and it did not work when plugged into a powered USB hub (only through the keyboard USB port and directly to the iMac).
Good news for portability… no need to lug a whole mixer or a substandard mic!