Well... of stories not mentioned yet. This is not a list of just good, but of any I could think of.
Ranma/Michiru
R-AA 'Coupled Union - Sea Breeze' by Silmarilis - [Status=Not Complete] - [Last Dld=12/19/2005]
Note: the Chained World Parent thread is very much Lemon oriented. But there were no Lemon episodes in the thread itself.
R-AA 'Chained World Shackled Sea' by HistorianoftheKais - [Status=Not Complete] - [Last Dld=01/04/2008]
Note: While the below link works, the story was never posted on that site. This was on the ill fated Fandorium site that went down quite some time back.
R-SM 'Elemental Air' by Brian Drozd - [Status=Single File] - [Last Dld=02/15/2004]
The below is more the beginning of a match.
R-SM 'Henko No Kaze' by Slade13 - [Status=Single File] - [Last Dld=01/05/2007]
Heh... Neptune is his mom in:
R-SM 'Moon Over Neptune' by Bob Lobster - [Status=Not Complete] - [Last Dld=12/21/2002]
A sort of Ranma/Michiru/Setsuna/Ami story
R-MULTI 'Prices Paid' by Ar-Kaos - [Status=Not Complete] - [Last Dld=01/04/2006]
Non-Lemon ones with the outers (or even all) include:
R-AA 'Tabula Rasa' by Multiple - [Status=Not Complete] - [Last Dld=11/25/2007]
Ranma/Haruka
R-AA 'Coupled Union - Racing Hearts' by Kender - [Status=Not Complete] - [Last Dld=08/19/2007]
R-SM 'Love's Rebirth' by Bob Lobster - [Status=Not Complete] - [Last Dld=01/08/2003]
R-SM 'Not Like You' by Lord CBoD - [Status=Not Complete] - [Last Dld=09/08/2007]
Not a match, but friends with benefits type deal with both Michiru and Haruka
R-SM 'The Reborn' by Innortal - [Status=Not Complete] - [Last Dld=04/16/2006]
Lemon ones with the outers (or even all) include:
R-SM 'All My Outers' by PsyckoSama - [Status=Not Complete] - [Last Dld=02/17/2004]
R-SM 'Endymion' by NekoXIII - [Status=Not Complete] - [Last Dld=10/13/2004]
R-SM 'Married With Scouts' by LS McGill - [Status=Not Complete] - [Last Dld=12/19/2003]
R-SM 'One Half a Neko Moon' by Chi Lord - [Status=Not Complete] - [Last Dld=05/02/2002]
Portions of the following lemon threads also apply:
R-AA 'Faking It' by Multiple - [Status=Not Complete] - [Last Dld=01/03/2008]
R-AA 'MND' by Multiple - [Status=Not Complete] - [Last Dld=04/17/2004]
R-AA 'Senshi Civil War' by Zaxxon - [Status=Not Complete] - [Last Dld=12/14/2006]
A few others occur to me, but cannot think of their names.