This [incomplete and ongoing] list of works organized by instrumentation [and/or ensemble size/type] will hopefully serve as a resource for performers, composers and researchers alike. Each composition's author links back to their page, where you can find more information.
Animated Notation [for indeterminate instrumentation]  :  Taavi Aher
Refurbishment [for indeterminate instrumentation]  :  Amenity Space
GoingPublik [for distributed ensemble and mobile score synthesis]  :  Arthur Clay
Children of the Seventh Species: Reveal Yourselves [for indeterminate instrumentation]  :  Alexander Dupuis
It's Not an Intervention [for indeterminate instrumentation]  :  Alexander Dupuis
more or less [for indeterminate ensemble]  :  Karlheinz Essl
bitsmoke: 2005 [for 4 performers of indeterminate instrumentation]  :  Casey Farina
bitsmoke [for 4 performers of indeterminate instrumentation]  :  Casey Farina
When Will It End [for indeterminate instrumentation]  :  Paul Farrington
4x4x4 [for any 4 instruments]  :  Luke Harris
Dozen it Make You Sick? [for indeterminate instrumentation]  :  Andy Ingamells
NYC_001 [for indeterminate instrumentation]  :  Antanas Jasenka
Animated Graphic Score 1 [for indeterminate instrumentation]  :  Leafcutter John
Point Studies no. 2 [for any 2 pitched instruments]  :  David Kim-Boyle
Point Studies no. 1a/1b [any 4 pitched instrument and computer or solo pitched instrument and computer]  :  David Kim-Boyle
Music for 4 [for any 4 instruments]  :  David Kim-Boyle
Music for 2 [for any 2 instruments]  :  David Kim-Boyle
Screenplay [for indeterminate ensemble]  :  Christian Marclay
The Bell and the Glass [for indeterminate ensemble of 2 or more]  :  Christian Marclay
Box Set [for indeterminate ensemble]  :  Christian Marclay
Pret-A-Porter [for indeterminate ensemble]  :  Christian Marclay
Chalkboard [for indeterminate ensemble]  :  Christian Marclay
Kvartett 7-15 [for somewhat variable quartet]  :  Guðmundur Steinn Gunnarsson
Kvartett 6: Koblakist [for somewhat variable quartet]  :  Guðmundur Steinn Gunnarsson
Kvartett 5: Deikokeitíponsa [for somewhat variable quartet]  :  Guðmundur Steinn Gunnarsson
Kvartett 4: Halanali [for somewhat variable quartet]  :  Guðmundur Steinn Gunnarsson
Kvartett 3: Sigliton [for somewhat variable quartet]  :  Guðmundur Steinn Gunnarsson
Hrammdæla 1-5 [for variable instrumentation]  :  Guðmundur Steinn Gunnarsson
Kvartett 2: Kvarandron [for somewhat variable quartet]  :  Guðmundur Steinn Gunnarsson
Kvartett 1: Lardipésa [for somewhat variable quartet]  :  Guðmundur Steinn Gunnarsson
Projected Notation [for 4 performers, indeterminate instrumentation]  :  Þráinn Hjálmarsson
LiquidScore [for any solo pitched instrument]  :  P. Hunter McCurry
Combat Music: games of strategic improvisation (Biplanes, Pong, Tanks) [for any 2 performers/instruments]  :  Cristyn Magnus
Akousmetria [for indeterminate instrumentation]  :  Alexander Ness
Dodging Bullets [for any instrumentation]  :  Keir Neuringer
Preludium [for indeterminate instrumentation]  :  Michael James Olson
Iridium [for indeterminate instrumentation]  :  Michael James Olson
Optical Scores [for indeterminate instrumentation]  :  Catherine Pancake
Flöskuhnakki / Bottleneck [for prepared plastic bottles]  :  Jesper Pedersen
White Lines (#1-#9) [for indeterminate instrumentation]  :  Marina Rosenfeld
My red, red blood [for indeterminate instrumentation]  :  Marina Rosenfeld
Reading [for indeterminate instrumentation]  :  Charles Ross
Sandbox [for indeterminate instrumentation]  :  Charles Ross
Volumes [for any instrumentation]  :  Jim Ryan
Tropical Fish Opera [for 4 indeterminate instruments]  :  Ramon Sender
Study no. 1 [spoke] [for 8 or more sustaining instruments]  :  Ryan Ross Smith
Study no. 2 [for vocalist, piano, and 4 or more instruments]  :  Ryan Ross Smith
Study no. 4 [big bear] [for 5 instruments]  :  Ryan Ross Smith
Study no. 5 [rainbow] [for 1 or more instruments/vocalists]  :  Ryan Ross Smith
Study no. 6 [escalators] [for 5 or more instrumentalists/vocalists]  :  Ryan Ross Smith
Study no. 11 [4+4] [for 4 performers with 4 distinct sounds each]  :  Ryan Ross Smith
Study no. 13 [for 2 or more performers with 4 distinct sounds each and electronics]  :  Ryan Ross Smith
Study no. 14 [duos] [for 2 performers]  :  Ryan Ross Smith
Study no. 28 [for up to 16 performers] [for indeterminate instrumentation]  :  Ryan Ross Smith
Study no. 39 [for 5 or more performers]  :  Ryan Ross Smith
Mad Scientist Machine [for indeterminate instrumentation]  :  Stefan Smulovitz
six cercles [for any 6 instruments]  :  Mike Solomon
Animated Scores 139-149 [for any instrumentation]  :  Andre Vida
LiveScore [for any number of performers and any instrumentation]  :  Harris Wulfson
tutti, duet, trio, solo, quartet [for indeterminate ensemble]  :  Justin Wen-Lo Yang