Layered Shader

Layered shader

Create your phong, blinn or whatever and map the color with the blend colors utility. It has three parameters: blend, color1 and colo2. Now, map the checker onto the blend parameter, and map the textures you want under color1 or color2. you will see one texture on the white boxes and the other on the black boxes. It's easy and fast to do if you want to mix a couple of textures via an alpha channel.
If you want to go deep ... you can map a second blend color on the color1 or color2 ... so you have three textures, mixed with two alpha channels. But if you want something in this way, I recommend you the layer texture utility:

open hypershade and create->utilities->texture->other->layered texture.

This is an interesting utility because it's full of utilities: add, in, out, substract, over, lightning, ... and it works in the same way that layered shader works. The output of this texture can be connected to any channel of your phong, blinn ... with just drag and drop.