Pulled this info up from the fanfic database (Theme=Crossover):

A FoLC\'s Revenge Karen Thompkins
A Slide Into Heroism Scott E. Johnston
Assignment: Gotham City Meinuk@aol.Com
At Wit\'s End in the East End Wendy Richards
By the Light of the Silvery Moon Elaine M Gustainis
California Cousin Marcus L. Rowland
Conflict of Interest David Schock
Death Is No Laughing Matter Scott Claybrook
Epic (Confusion) Robert Culpepper
Finding Lois Lane Bluegrlfairie
Five Crossovers That Never Happened To Lois and Clark Marcus L Rowland
Forever Superman Anne Spear
Gift of the Magami Lady Tesser and David Schock
Heroes Helping Heroes April Flager
Lois and Clark and Silver and Bruce Phil Atcliffe
Lois and Clark/Quantum Leap Crossover Michael Chary
Lois and James: the New Adventures of 007 Jonesy321
Misadventures Again Marnie Rowe
Misadventures in Crimefighting Marnie Rowe
Offending Maggie Tara Smith
Power Dreaming Mrs. Luthor
Purple Chaos Emily M. Hanson
Remnants of Chaos Emily M. Hanson
Shades of Chaos Emily M. Hanson
Superheroes Got to Look Out for Each Other Too Rachel White
Superman Meets Larry Boy Carol Moncado
Superman -V- Batman: An Unlikely Scenario Debby Stark
That Peanuts Gang of Mine Judith Williams
The Meeting Jason Ashton
The Spider and the Fly (Boy) Robert Culpepper
The Supergirl Chronicles: Power of the Past Dyann Vaccaro
The Weakest Link Barb Pillsbury
The Wonder of it All Tank Wilson
Threads Of...Barbeque? Tara Smith
Timeless Becky Bain
To the Stars Carolyn B Schnall
To the Stars Elaine M Gustainis
Top Secret Julie L. Jekel
Two of a Kind Joe Crowe
Two of a Kind Jon B. Knutson
Unlikely Encounter Skylark
World\'s Finest Craig Byrne and Matt Coombes
X File Case #1913114 Dawn Field
Your Little Secret Shawn V
A Flash in the Pan Ben Pistorious
All-Star Pickup Game Joseph Barrow
Avatars Joel Schuldt
Chaos Revisited Emily M. Hanson
Cold Fire Cybercerpent
Couch Potatoes Phil Atcliffe
Cousins Skip Davis
Destiny Joel Schuldt
Face/Off Shawn V
Faith, Hope...And Reward Tank Wilson
Firing Squad Anne Ciotola
Flash(Back) Robert Culpepper
Forever Young Shayne Terry
How I Spent My Summer Vacation Cindy Leuch
Hunter\'s Moon Laura Davies
Hunter\'s Vengeance Laura Davies
Hunting Weather Laura Davies
Intervention David Schock
Junkyard Wars Richard Frantz Jnr.
Lois and Clark Meet the X Files Zoomway
Not Again? Shayne Terry
Sins of the Past: the Saga Continues Joel Schuldt
Some Like It Hotter Dave Songer
Storm Warnings Joel Schuldt
Super Friends Sheila
The Bodyguard Francis Syl
The Chicken or the Egg? Jenny Stosser
The Electrified Bride Allison K. Forbes
The Flash Kyle Harper
The Letter David Schock
The Metropolis Files Carrie Smith
The Old Shell Game Joel Schuldt
The Power of Shazam Craig Byrne
The Return of Brainiac Jon B. Knutson
The Vision Emily M. Hanson
Web of Steel Paul-Gabriel Wiener
A Clean Break Mary Potts aka Queen of the Capes Aka Queen Of The Capes
Code of Honor Dawn Field
Death Takes a Holiday David Schock
Deranged Mutant Killer Monster Snow Goons of Smallville Phil Atcliffe
Everyone Has An Angel Betty Huang
Flash Fried Paul-Gabriel Wiener
Lois and Clark Meet Back to the Future II LNCTNAOS
On the Bright Side Laura Davies
Speeding Bullets Zoomway
Swapmeet: Metropolis Margaret Brignell
The Forgotten Folk Anne Spear
Creatures of the Night Joel Schuldt
Escape From Krypton? Hazel
Faith, Hope...And More Hope Tank Wilson
From the Stars Carolyn Schnall
I Only Have Oz for You IRC Round Robin - Various
Lois and Clark Meet Back to the Future I LNCTNAOS
Something in Common Barbara
Threads of Confusion Tara Smith
Twilight of Youth Joel Schuldt

Hope that helps!
Jo