Lens that fit nikon d3100?

Besides nikkor lens, maybe like tamron or sigma

Most of the major third-party lens manufacturers make lenses for the D3100, like Sigma, Tamron, Tonika, etc.

You just have to make sure it is a Nikon F mount and it has an in-body focusing motor (AF-S).

I wouldn't waste money on aftermarket lenses though. Nikkor all the way.

For Sigma, I believe you need HSM (internal focusing motor)

For Nikon, you'll need AF-S (internal focusing motor)

Bear in mind the need for that internal focus motor when you are shopping around. Amazon.com and Adorama.com are great places to start.

Hope this helps!
Chris at http://www.chrisaram.com