1, Use Nikon Capture 4 editor ($100 in 2005). There is a D-Light button built in, whih is HDR ((High Dynamic Range) if your photos are in JPG or RAW files). If you take photos in RAW file, there are more to modify your photos after your photos being taken.
2, Use Nik Efex plug in. Several years ago, Google bought the company and set it as a free software. But right now some webs are selling the software.