2hotspot parece fazer o que você pergunta:
De 2hotspot:
A powerful software that enables the instant creation wireless hotspots using your wireless router or WIFI card. With this free software you can, run your own free or commercial wireless hotspot network; Create local wireless communities where bulletin board, chat, and forums available locally with or without Internet service; Share your broadband service, split your ISP bill, control shared bandwidth; Used by individuals & corporations.