LinPopUp is a X11 port of Winpopup,
running over Samba. It permits to communicate with a
windows computer that run Winpopup, sending or receiving
message. (It also provides an alternative way 
to communicate between Linux computers that run Samba). 
Note that LinPopUp is not only a port, as it includes 
several enhanced features.

WWW: http://www.littleigloo.org/