What I really like is wrapping my dick in a fat girls fat after I've fucked her into submission.  Not just her navel, but her soft squishy fat, where ever it may be.  With my girlfriend, mostly I wind up under her skirt, where I cum frequently.  However, I've also cum in her navel, her arm pit, between her upper and lower bellies and in the fat on her sides, under her breasts.  Anywhere soft, hot and lubed will do. 

 However, I seem to be just about the only one into it.  I've only seen my fetish captured on film a few times.  There are a lot more images of navel fucking, but unless you're really small, you can't get all of your dick in a navel.  I'm not huge, but I've got more than a navel full.