Recommendations for a portrait lens for NikonD90?

I have been doing portrait photography for some time and am looking to purchase a lens that will improve my photos. I have a Nikon D90 and currently have the standard starting kit lens. I would love to get a lens that produces great bokeh. I would love any recommendations, thank you!

Something with a large aperture. Try 50mm 1.4 or 50mm 1.8 as a cheaper option

Usually, anything between 50 and 105 MM is considered portrait length. However, almost any length is usable depending on the effect desired. On a full-frame camera, 85MM is considered the "ideal" length.

Bokeh is a matter of focal length, aperture, and focusing distance. The 85MM f1.4 is often considered the "cream machine" because of the super smooth bokeh. The bokeh of the 50MM f1.4 is far better than that of the f1.8. Of course, the f1.4 of either lens is more expensive than the 1.8 model. Nobody ever said photography is a cheap hobby.

Using a long lens and close focus is a way to get DOF down to manageable levels. I was out today and shot a squirrel using a 300 MM lens at f8. Focus distance was about 10 feet, and DOF was under 1 foot, giving me a focused squirrel and everything else out of focus. A large aperture isn't always necessary.

http://www.dofmaster.com/dofjs.html will let you enter various focal lengths, apertures, and focus distances and give you a total DOF. Too little DOF and your entire picture looks out of focus. Too much DOF, and you have too much in focus. Play around with the numbers, and get an idea what does what.

Great bokeh, 50mm f1.4 or 85mm f1.4. Possibly sigma's 50mm f1.4