http://www.techtv.com/screensavers/downloadoftheday/story/ 0,24330,3647418,00.html

One of the most helpful programs to the cross platformer out there. It allows you to use the same mouse and keyboard for more than one computer using a network(rather than a hardware switcher) almost just like you where using a multi desktop setup with dual moniders. It currently only works with linux and windows, but mac support will probably be made soon. It is just so cool. Easy to install and run on both windows and linux(it is aimed to redhat, but i believe it can be install on other distros, just not so easy.)