InterComm for Mac

From Five Across:

InterComm delivers next-generation instant messaging features integrated with file sharing. InterComm is organized around the groups in your life: your family, your friends, and the people you work with. Ordinary instant messengers organize all these contacts into one list where you're either online or offline to all. With InterComm, your contacts are organized into groups, complete with a file sharing repository for exchanging important group documents. InterComm is the only IM software with selective availability - control over which groups can see you online, on a group-by-group basis, and the only IM software with built-in file sharing.