Nell co-wrote the score to Legally Blonde, the Musical with composer Laurence O'Keefe, which received Tony Award nominations, Drama Desk nominations, and the Olivier and Helpmann Awards for Best Musical.

Nell wrote the lyrics to Mean Girls, which received multiple Tony Award nominations, including for Best Original Score and Best Musical.

Nell's play, The Explorers Club, won the Outer Critics Circle Award for Outstanding Off-Broadway Play, the Edgerton Foundation New American Plays Award, and an Alfred P. Sloan Foundation grant.

Nell has written book and/or lyrics for Pirates! (or Gilbert and Sullivan plunder'd), Sarah, Plain and Tall, Cam Jansen (Drama Desk-nominated), I Want My Hat Back, How I Became A Pirate, The Mice, Life of the Party and Because of Winn Dixie.

Upcoming musicals are: Huzzah!, Life of the Party, Dave. 

Television writing includes "Unhappily Ever After", Animal Planet's "Whoa! Sunday with Mo Rocca", "Electric Company", "Best Time Ever with Neil Patrick Harris", "Ant & Dec's Saturday Night Takeaway", "Julie's Greenroom." 

Benjamin is the recipient of the Kleban Foundation Award and a Jonathan Larson Grant.