Combined camera lenses?

I recently purchased a Nikon D3100 and since i travel alot i want a combined lense that is 18mm to 200mm. What kind of lense should i consider that is affordable, but still good quality?

Nikon's 18-200 is the best. Sigma's 18-200 OS isn't that bad and significantly cheaper. Think if you really need 200mm. Nikon's own 18-105 and 18-135 are very nice lenses and affordable, the 18-135 is a steal on the used market