Any advice on a lens for Nikon D3100 18-55 VR Kit?

I'm looking to take photos of landscapes throughout Europe. This is for fun. I'm completely new at this. I'm thinking of getting a full-frame fisheye lens. However, I need some advice on picking one thats good and can be used with my camera. Any advice? Links to the lens are appreciated.

My advice? Forget the fisheye! It will cost more than your camera. I'd look at a 55-200mm to add on to the 18-55mm you already have.

Unless you really have an artistic vision and reasonable expectation of how a fisheye lens could serve it, that is not the best use for your money.
However, if you really want one, this is probably a good choice:
http://www.bhphotovideo.com/...EX_DC.html
As a DX lens it should give you good fisheye effect on your DX sensor. Also, this Sigma is an HSM model (equivalent to the Nikon AF-S), and it would autofocus with your D3100. Currently I don't think any of the Nikon brand fisheye lenses are AF-S.
As for capturing landscapes, a fisheye lens does not only have super barrel distortion, it also has super perspective distortion. What is very close to you looks big, but what is on the horizon looks tiny.