RANMA-XMEN 'Abnormality' by Matdeception - [Dld Date=08/12/2011] - [Dld Size=27kb] - [Dld Status=Inactive - Preview]
RANMA-XMEN 'Contracts Snippet' by Matdeception - [Dld Date=11/11/2008] - [Dld Size=9kb] - [Dld Status=Inactive - Preview]
RANMA-XMEN 'Ranma 12 X-Change Students' by H Torrance Griffin - [Dld Date=09/26/2002] - [Dld Size=190kb] - [Dld File Cnt=3] - [Dld Status=Inactive]
RANMA-XMEN 'Ranma Evolution' by SSJ Guyver1 - [Dld Date=10/24/2004] - [Dld Size=22kb] - [Dld Status=Inactive]
RANMA-AA 'Ekusu-Hito' by Multiple - [Dld Date=07/29/2010] - [Dld Size=969kb] - [Dld File Cnt=145] - [Dld Status=Inactive]
RANMA-AA 'Ranma Evolution Lower' by Multiple - [Dld Date=09/03/2005] - [Dld Size=492kb] - [Dld File Cnt=61] - [Dld Status=Inactive]
RANMA-AA 'Ranma Evolution Upper' by Multiple - [Dld Date=10/16/2007] - [Dld Size=415kb] - [Dld File Cnt=83] - [Dld Status=Inactive]
RANMA-AA 'Ranma Ultimate Evolution' by Multiple - [Dld Date=01/02/2008] - [Dld Size=50kb] - [Dld File Cnt=7] - [Dld Status=Inactive]
Be aware, there is only a slight cross into XMen in the following stories, not sure count:
RANMA-MULTI 'Neko' by Angel Frog - [Dld Date=06/30/2006] - [Dld Size=222kb] - [Dld File Cnt=17] - [Dld Status=Inactive]
RANMA-AA 'Enforced Evolution' by Multiple - [Dld Date=04/26/2013] - [Dld Size=1497kb] - [Dld File Cnt=144] - [Dld Status=Inactive]
Not sure if the below are in the X-Men section on FF.NET or not. Technically, they are not really XMen crosses per se, but City of Heros crossovers.
RANMA-COH 'A Hero's Awakening' by Agnostics Puppet - [Dld Date=10/18/2007] - [Dld Size=217kb] - [Dld File Cnt=5] - [Dld Status=Inactive]
- - [MD Source=FF.NET] - [MD Rating=T] - [MD Word Cnt=40006]
- - [MD Summary= [City of HeroesRanma 12] One day after the fiasco of the failed wedding Ranma attempts to save a strange girl. Unknowingly he recieves a gift from her that will change his life forever. Teen for now.]
- - [Direct URL] https://www.fanfiction.net/s/3827700/1/
- - [Author1 URL] https://www.fanfiction.net/u/325962/
RANMA-COH 'Revelations and Regrets' by James Rennfield - [Dld Date=10/09/2007] - [Dld Size=27kb] - [Dld File Cnt=2] - [Dld Status=Inactive]
- - [MD Source=FF.NET] - [MD Rating=M] - [MD Word Cnt=5270]
- - [MD Summary= The path of a martial artist is fraught with peril. These words would always ring true in the ears of one Ranma Saotome. And when Ranma travels to Paragon city in search of a cure along with Nabiki he would find out how true it is. RanNab CoHXover]
- - [Direct URL] https://www.fanfiction.net/s/3820175/1/
- - [Author1 URL] https://www.fanfiction.net/u/1368785/
Not sure if the below are in the X-Men section on FF.NET or not. Technically, they are not really XMen crosses per se, but multi- crossovers.
RANMA-MULTI 'Chaos and Carnage' by Gundraw - [Dld Date=10/23/2006] - [Dld Size=439kb] - [Dld File Cnt=12] - [Dld Status=Inactive]
- - [MD Source=FF.NET] - [MD Rating=M] - [MD Word Cnt=81585]
- - [MD Summary= What if the symbiote spawned from Venom had another trait acquired from one Peter Parker... the one to protect the masses and that there is a responsibility with the power it has. And what if it somehow stumbled upon our young Pigtailed Protagonist?]
- - [Direct URL] https://www.fanfiction.net/s/1643005/1/
- - [Author1 URL] https://www.fanfiction.net/u/376785/
RANMA-MARVEL 'Prime Attitude' by CRose - [Dld Date=04/26/2004] - [Dld Size=374kb] - [Dld File Cnt=6] - [Dld Status=Inactive]
And since it was mentioned...
RANMA-MULTI 'Just won't die' by Jeffrey OneShot Wong - [Dld Date=05/31/2006] - [Dld Size=14776kb] - [Dld File Cnt=33] - [Dld Status=Inactive]
EDIT: It was already given, but I realized my own link to it is not the same as the one provided by the above member:
RANMA-XMEN 'The Evolution' by Lu Dragon Lord - [Dld Date=11/17/2002] - [Dld Size=373kb] - [Dld File Cnt=2] - [Dld Status=Inactive]