On it's own little note, I recently was able to obtain an incredible lens for an incredible price. I work in a little camera store, and someone traded in a 105 mm f/2.8 Macro lens. I was ecstatic and snatched it up before anyone could take it. It's an incredible lens because of the long focal length and the fact that it's macro. It's amazing for portraits as it compresses people and doesn't make them look wider than they are. You, as the photographer, are also not in their face taking photos which can cause the subject anxiety (unless you're taking photos of peoples eyes, then it's terrifying).
Esme's
Sarah's
My eyes (taken by Esme Brandon ©)
Obviously distance is a factor in depth of field (DOF), so the closer I get to an object, like a flower or a bug , the less is in focus. I had to learn that the hard way when I photographed an object at school close in and didn't realize that some of the object would be out of focus. I needed to close up my aperture if I wanted more DOF.
In mexico there were a few really massive bugs we would see during the day, and I got really excited the day there was one right outside our room. So I got this lens out and got right into this giant bug's face as it climbed around the stairs. I think I really ticked him off because he tried drowning in a puddle.
Anyways, if you're a Nikon user, and you need a macro, I would HIGHLY recommend the 105 f/2.8 Macro lens. You won't have buyers remorse.