As my 20" iMac is out for repair (bad graphics chip, apparently. Under applecare. Thank god...) I am using my MBA as a substitute temporarily. Here is the setup: USB Port: 7-port USB hub: two printers; ethernet adapter to router; 2 external hard drives - one of which has two partitions (the Superduper clone I am booted to (copy of the iMac) and the External iTunes library; one iPod sync cable; one eyeTV USB connector. Micro DVI to VGA adaptor to external monitor. Audio Out: External speakers. Pretty good for three on-board ports, huh?