Manhattan USB-A to 4x Serial Port Converter, Male to Male, Serial/RS232, MosChip MCS7840, Automatic IRQ and I/O address selection, Bus powered, Silver, Boxed | www.uk.shi.com
Moschip MCS7830 USB to Ethernet Adapter for around $10 | MacRumors Forums
4-Port USB Server IP NetUSB Titan RJ45-400i (Moschip) - Cablematic