I got a Linkskey KVM on newegg a while back for about $30 new. It has 2 USB ports, VGA, and works great with my powerbook and PC. Its been about 6 months with no problems.
The only problem is that New Egg no longer has them for sale.
But, after a bit of Googling, i found it
here.
Not sure about the retailer though, but maybe you can find the same KVM somewhere else.