You will always get advice about lights, but very few seem to mention the importance of a reflector. A reflector can act as a secondary light source and make all the difference to a photograph. It can be just a sheet of white card or card with tinfoil stuck to it, or it can be a proper reflector. these are only about £36 in UK so maybe $40 in US or even cheaper. You will have a white, silver, gold and black reflector. This can just bounce light in, warm it up, kill it off (black) or act as a diffuser (white). Please do consider getting one, it can make all the difference to an image and enable you to get great shots with an off the camera SB800 or SB900.
AS for the lens it depends on what sensor you have. If you have an APS sensor with a 1.5 multiplier then something around 50-70mm will give you the best and most flattering effect. If you have a full sensor (D700, D3 etc) then something around 100m to 135mm will give the best and most flattering effect. I ten to use my 105 micro lens on my D700. Although it is normally for Macro work it has excellent glass and gives a really wonderful portrait because of the focal length. A lens of around 35mm CAN give slight distortion (wide angle effect) on APS sensors and even more so on Full sensors.