Limelight Series

Works based entirely around featuring forgotten and abandoned sections of the canon and going beyond A Day in the Limelight but making an entire Ensemble Cast of Ascended Extra / Ensemble Darkhorse characters.

Examples of Limelight Series include:

Anime and Manga

Pokémon Chronicles, a Spin-Off of the Pokémon anime centering around characters that had been Put on a Bus, including Misty, Tracey, Richie, and various One Shot Characters.
The various gaiden manga series for Fist of the North Star are these, with different miniseries for Raoh, Toki, Rei, Jagi, and Juza, currently.

Watchmen was originally supposed to star a team of Charlton Comics superheroes, though that plan was cancelled when it was decided to integrate said characters into the DC Universe at large.
Marvel Comics' The Defenders, for most of its versions.
DC's The Outsiders too.
DC's Gotham Central focuses on the Gotham City Police Department with only cameo appearances by Batman, the Joker, etc.
Archie's Sonic Universe, which focuses on anyone not named Sonic the Hedgehog (and even then, he can take center stage!) and allows for storylines that can't be fit into the main comic to be addressed.

Epic Mickey.
The (sadly Japan-only) Wii game Captain Rainbow, in which the player controls a superhero who has to fulfil the wishes of a bunch of Z-List Nintendo characters, including Birdo, Little Mac, a platoon of Advance Wars soldiers and Lip from Panel de pon.

Batman the Brave And The Bold, which, among other services to the DC Rogues Gallery, made a Memetic Badass out of Aquaman.
Justice League Unlimited gave plenty of screen-time to minor and B-Level DC Heroes, with Character Focus on Captain Atom, Green Arrow, Black Canary, Huntress and The Question, and plenty A Day in the Limelight episodes.