Neil LaBute, Stephen Adly Guirgis, Wendy MacLeod (“The House of Yes”) and Julia Cho (“BFE”) are among the scribes contributing new plays to Ensemble Studio Theater’s Marathon 2007, the theater’s 29th annual fest of one-act plays.Marathon is the first in the wake of the January death of E.S.T. founding a.d. Curt Dempster. William Carden recently took the reigns at the org. Fest is divided into two evenings of five plays each. First group — including the pieces by LaBute, Cho and MacLeod — runs May 31-June 20, and the second, which has one-acts from Guirgis as well as Peter Sagal and Daniel Reitz, runs June 15-June 30.