I did take a look at the site you are referring to (great photos by the way), and none of those can be considered macro shots. There are merely close-up shots of very small subjects.
The photographer himself state that they are shot using a fisheye lens in order to get so much of the background. He is also very to the miniatures when shooting. There are a few pictures of him shooting on the faq page.
So if you want to do something similar to him, you should use your widest angle, i.e. the 18-55, set it to 18mm, and the largest possible aperture, f/3.5.
You might have a problem being able to focus close enough, in which case you could invest in a set of inexpensive extension tubes. These are simply a set of tubes that you put between the lens and the camera. There is only air, so it will not degrade image quality. And they will allow you to focus closer to the lens, at the expense of not being able to focus on subjects far away.
p.s. This is actually the exact opposite of the currently accepted answer, but this is based on the example site that you linked to.