If you decide to go with a longer lens and find that you like it (and either the 105mm f/2.5 or 100mm f/2.8 are good lenses to try), I'd suggest you look into a 28mm f/2.8 AIS lens next. It's the best (in my opinion) of the Nikkor wide angle lenses for minimized distortion and resistance to flare. My standard "kit" when I'm travelling light includes the 105mm f/2.5, the 28mm f/2.8 (AIS only...not the older AI), and the 50mm f/1.8. (I like the f/1.4, but don't do enough low light shooting to justify owning one myself.)
There are a lot of great Nikkor lenses out there, and if you're happy with manual focus you can get staggeringly good glass for very little money. The pages on Nikkor lenses that start at http://www.mir.com.my/rb/photography...rces/index.htm have more information than you'll ever need on just about every Nikkor lens ever made.