What type of lens is good for portraits/close ups? (Nikon)?

I like to photograph nature up close. I have a 18-55 lens and can't capture exactly what i'm liking to. I also want to be able to take portraits. What lens would be good for me?

I don't want to spend more than 400$ Unless the answer is Really good and I do research and fall in love with the product. So any recommendations/reviews are welcome!

Added (1). Ps: I have a Nikon D5000

You're actually writing about two different lenses.

Portraits - you can use virtually any wide lens - I use a 28-200.

Close ups, or "macro", require a macro lens. I'd suppose you could try portraits with a macro lens though. Lighting is important in any case.

Perhaps the 60mm AF-S micro (micro = macro in Nikon speak) lens. At f/2.8, it's useful for portrait work. For shooting critters close up, you would be better off with the 105mm micro lens to give enough distance so you don't disturb the critters. 105mm is a bit long for portrait work unless you have the space.

Cost for the 60mm lens is around $550.