There are two things you can do. First get a zoom lens that has a macro feature. You will actually have to further away from the object you want to take a picture of, but because of the zoom capabilities and macro feature it will look like you were on top of it.
Second you can get a dedicated macro lens. I have a 50mm prime lens for my Canon that allows me to take pictures as close as about 6" from the object. It take amazing pictures and was not horribly expensive. I actually need to sell it because it wont work with my digital Canon.
However there are pros and cons to each set up.
With the zoom lens you can take advantage of the natural or existing light, but you dont get the details that you would with a dedicated prime lens.
With the prime lens (50mm macro for example) you cast shadows on what it is your photographing because you can get so close. But you get amazing details of what it is you are taking a picture of. I took a picture of a spider on a flower once with my 50mm lens. The spider wasnt a 1/4" in size but you could make out the tiny hairs on its legs the details were so good. I wouldnt have been able to do that with zoom lens with a macro feature.
I use my 70 - 300mm lens with a macro feature to take close up pictures of things that may be a little skittish, like butterflies. I can get the butterfly to fill up the frame but I loose a little in the details of the designs on each one.
Hope this helps out some.
