Details:

Can sniff any interface that has got an IP address, including 127.0.0.1 (localhost/loopback)
RawCap.exe is just 17 kB
No external libraries or DLL’s needed
No installation required, just download RawCap.exe and sniff
Can sniff most interface types, including WiFi and PPP interfaces
Minimal memory and CPU load
Reliable and simple to use

Download:
http://www.netresec.com/products/RawCap/RawCap.exe