What are good lens to upgrade to from 18-55mm?

I have a Nikon D3100.

Depends on your budget. Some suggestions:
AF Nikkor 50mm f/1.4D
AF NIKKOR 50mm f/1.8D
AF Zoom-NIKKOR 70-300mm f/4-5.6G
All economical lens, none will auto focus on D3100 but good lens to practice photography.

There's the Nikkor 17-55 mm f/2.8, but you will not like the price… $1, 540

Maybe what you should consider is buying a second lens that either is wider than the 18-55 mm like the 10-24 mm or longer. The longer lens can be used for shooting sports, action, air shows and some wildlife. Those would be the Nikkor 55-200 mm VR, 55-300 mm VR or 70-300 mm VR lenses

Here is a link to all the available lenses… Just remember that you need to look at AF-S lenses so that your D3100 can auto-focus with it.

http://www.nikonusa.com/...index.page

Well it depends on what you need. What focal length do you use most? 18 or 55? If you use 55 a lot get a mid range prime, if you use 18 a lot get a wide angle prime. Or you can try out a telephoto. But really, any lens at all is an upgrade from an 18-55 kit lens because an 18-55 kit lens is the absolute worst lens possible.