It's been a while since I updated the list here so I'm reposting the whole thing.
Drakensis
The Taurian Gambit: Hanse allies with The Taurians during the Fourth Succession War opening a new front against the Capellans.
One Letter: Janos Marik invades the CapCon during the Fourth War in revenge for Max Laio's instigation of Anton Marik's revolt.
A Victorian Age: What if Victor Steiner-Davion was born a girl?
Star Adder Symphony: Clan Star Adder decides to participate in the invasion of the Inner Sphere with typical Star Adder style. With lots of logistical planning done well ahead of time.
Riding the Dragon: Takashi Kurita and his entire family actually get killed in one of the several failed assassination attempts. Things change rather radically.
Battlestars and Battlemechs: New Battlestar Galactica/Battletech crossover
Bolotech-Pillar of Steel: Bolo/Battletech Crossover Part 1
Bolotech-High Ground: Bolo/Battletech Crossover Part 2
Davion & Davion (Deceased): Hanse Davion's ghost goes back in time to the last days of the Star League.
master arminas
Kerensky and Kurita: Book 1
Kerensky and Kurita: Book 2 Blood and Steel
Kerensky and Kurita: Book 3 The Long Road Home
Scorpio Ascendant: Scorpion led Clan invasion of the Inner Sphere
The Seeker A story about a Goliath Scorpion seeker in the Inner Sphere.
Operation Revival Reborn: An all Clans invasion of the Inner Sphere aimed solely at the Lyran Commonwealth to start.
The Wobbly Guy
New World Order
Seekers in Shadow
The classic Wobbly Guy stories about a rag tag group of multiple mercenary companies finding something in the periphery and the Clans tag along for the ride of course.
Tokage
DARIUS AND THE HOUND
THE MISADVENTURES OF DARIUS DAVION
DARIUS AT THE CORONATION
DARIUS AND THE HAPPY OCCASION
DARIUS AND THE HEARTBREAKER
The Darius Davion Stories, part comedy and part action.
Takiro
Clarion Call: Instead of Dieing of that heart attack Hanse Davion gets a vision of everything that happens through the Word of Blake *****.
Davout73
Interview with a Mercinary: A series of interviews with a mercenary group.
Kiiro no tori: The battle on Halstead Station goes a little worse and the FedCom states focus the Fourth Succession War against the Draconis Combine instead of the capellan Confederation.
Evil Author
Reuinions Are Hell: New Battle Star Galactica crossover with Battletech (The 12 Colonies and the Star League)
Fifth Column: Wacky nBSG/Battletech crossover
Tales of the Outer Sphere:Spinoff/Side story of above.
Hotpoint
Hunted Tribes: nBSG/Battletech Crossover
But somehow a most melancholy: A spinoff of Hunted Tribes written with Cannonshop
Trace Coburn
The Virginia War Meeting - Engagement
The Virginia War - Ense Petit Placidam...
The Virginia War - Pieces of War
Battletech/nBSG/Tom Clancy
Keiran Halcyon
Exodus of Stars: The Exodus Fleet runs into the the Quarian Migrant fleet from Mass Effect.
Hammer6R
Drakes Demons, Book 1: Comes A Jolly Roger: Mercs vs the Tortuga Dominions
The American Group: Drumbeat
Thunder of Eagles
sharlin
Battletech ASB story: The Exodus Fleet jumps to the real world.
Necrosiac
With Impatient Fury, Winter Comes: The Ice Hellions get impatient and invade early. Early Clan Invasion with a single Clan.
The Blizzard: updated version of the above story with a modified invasion plan
Cray
Planets
Aethra: One Weird Planet
The Sunless Sea
Sweet Home Savannah...
Dealing with the Devil
St. Croix Defenders
Stories
And Please Sign In Blood
I Regret To Inform You...
Comstar *****
Comstar *****: The Freighter That Conquered Worlds
M-7 Main Battle Tank
XBM-1 Miyogi
BM-3 Tarag
Gladius-class "Battle" Carrier
Rasalhague-class fighter carrier
Cannonshop
Traveling with Cousin Giao
A Sickness (Ngoverse/FGC'62-91 tie-in)
"*******" (FGC based AU)
Dinner With Elizabeth (FGC AU)
A Singular Event (FGC translation)
Slouching to Independence (FGC AU)
Chickens come Home To Roost (FGC AU)
theoreticalchaos
A Drunken Nerd in Janos's Boot's (A Battletech SI): SI replaces Janos Marik in 3014