Best Lens for Nikon D7000?

A lens that makes the background blur ALOT. How do i pick a lens that blurs the background alot?

Added (1). Please suggest nikon lens under 1000$ :)

Added (2). I currently have a 18-55 lens… It doesn't make the background blur that much.

To blur the background A LOT, get this:
http://www.bhphotovideo.com/..._1_4G.html
To blur it almost as much, you could get this:
http://www.bhphotovideo.com/..._1_8G.html

Here is what you need.

* use a medium telephoto lens like a Nikkor AF 50 mm f/1.4 or AF-S 85 mm f/1.4
* shoot with the aperture wide open
* place the subject as close to the lens as the lens will focus

The best lens for $1, 000 is the Nikon AF 80-200mm f/2.8. You can get very shallow DoF at f/2.8, and at 200mm, depending on the focus distance, you can get DoF as shallow as a couple of inches. And at these DoFs, the lens has outstanding "cream cheese". Or milky smooth bokeh - however you want to describe it.

You just can't beat focal length for the best shallow DoF photography, and at 200mm, it is far better than shorter lenses. For shallow DoF, focal length is the most important, followed by focus distance, and finally aperture.

Plus it is a pro-level lens, and very good for sports photography.

I have one that I use on my D90, and here are a few photos and a web page with photos I took with this lens and my D90 showing the great bokeh.

http://www.althephoto.com/lenses/pro-telephoto.php

And here is a webpage comparing the bokeh between a Nikon 50mm f/1.8. Nikon 18-200mm @ f/5.6, and the Nikon 80-200mm @ f/2.8.

http://www.althephoto.com/concepts/selectivefocus.php

You will be able to see that the Nikon 80-200mm has vastly superior bokeh over the other lenses. The background with this lens is completely blown out.

In fact, the Nikon 80-200mm is one of the best lenses ever made by Nikon, and as long as you have a camera such as your D7000 that will autofocus an AF lens, it is a killer pro lens on a budget.