It's a bit difficult to recommend a lens without knowing any of your shooting types, but there is a plethora of lenses great for all of the categories that you mentioned.
For a prime, I'd recommend either the great 35mm f/1.8 DX, which gives an equivalent of about 50mm, or the 50mm f/1.8 (which isn't yet available) and will give a focal length of 75mm, better for portraits but still great for day-to-day shooting. Alternatively, consider the 50mm f/1.4, which is available as of today and gives 2/3 of a stop more light.
If you/re happy with the 18-55, I don't see any reason of upgrading, it's a pretty good lens for a kit. If you do want to upgrade, consider the 16-85 or the 17-55 f/2.8. The 16-85 is a good alternative if you want a sharper, all purpose lens that will give you more coverage, and the 17-55 is better for low light (but expensive, and could give your D3100 an unbalanced feel).
Nikon offers two wide angle zooms for the DX format, the 10-24mm and the 12-24mm. The 10-24 is wider (and yes, the 2mm DOES make a big difference), cheaper but has a variable aperture of f/3.5-4.5 and isn't built as well. The 12-24 is fixed at f/4, and had a better build and less distortion. Optical quality wise, they both perform the same at their widest but when the 10-24 reaches 12mm, it performs better than the 12-24. Of course, when you correct the 10-24's distortion afterwards, it will pass 12mm. It's really your call. There's also the f/2.8 10.5mm fisheye, but it's more of a special purpose lens.
For a telephoto lens, the 70-200mm is the best way to go, but it will outweigh your D3100 like crazy. Take a look at the 70-300mm, it gives an equivalent of 105-450mm, and it's optical quality is pretty good for the price.
Hopefully I helped in your search for a new lens!
Gear: 7 Nikon Nikkor AI-S and AF-S lenses, SB-700 flash, Nikon D7000, Nikon FM, variety of accessories
"There are no rules for good photographs, there are only good photographs."
- Ansel Adams