You need a layer 3 device in order to make them communicate. It can be a Linux box with two NICs, as betty85 has stated (although I wouldn't use masquerading), it can be a router, it can be a layer 3 switch... They can all help to make your subnets see each other, but which one is right for you depends on your more specific needs. If you have a tight budget, get an old pc and use Linux to do the routing. If you plan to make many more subnets, I'd pick the layer 3 switch route.
