ArpTools

ARP Tools is collection of libnet and libpcap based ARP utilities. 
It currently contains ARP Discover (arpdiscover), an Ethernet scanner 
based on ARP protocol; ARP Flood (arpflood), an ARP request flooder; 
and ARP Poison (arppoison), for poisoning switches' MAC address tables. 

There's two slight problems with this request. I mean, it looks like a great package, but I believe this forum isn't meant for requesting "ports" to Windows from *NIX apps.

The other thing that, even IF this had a Windows counterpart, it could not be a PortableApps.com portable app because it uses libpcap, which pretty much means it has to be installed with administrator privileges, yada yada... check the "wireshark portable" request for more info.

/sylikc