Fanfic: "It Can't Be Helped" by InHerOwnWorld (Not finished.)
Summary: In which Nick exhibits vulpine tendencies and Judy is oblivious to what they mean.
Link: http://archiveofourown.org/works/8668324/chapters/19871509

Fanfic: "Winter Snuggles 1" by Boney_M
Summary: An assignment in Tundratown causes the already-close relationship between Nick and Judy to grow closer. And not just for warmth.
Link: http://archiveofourown.org/works/6933031/chapters/15814879

Fanfic: "Winter Snuggles 2" by Boney_M (NSFW continuation of previous.)
Summary: In stark contrast to the cold outside, things between Nick and Judy are heating up. Made into a separate story to increase the rating to M.
Link: http://archiveofourown.org/works/7626403/chapters/17361715

Pretty much everything by Kulkum (Really great stories with a lot of gratuitous naughty along the way.)
http://kulkum.deviantart.com

And more, but that's decent share for now.