Yes, Foxface's real name, Finnick Odair, is mentioned in the book "Catching Fire" by Suzanne Collins. It is revealed during the Victory Tour when Katniss and Peeta visit District 4.
Foxface's real name in "The Hunger Games" series was never revealed. She was known only by her nickname, Foxface, due to her sly and cunning nature as a tribute in the Hunger Games.
In the book "The Pact," Caveman's real name is James.
in the book wringer Henry's real name is george
In the Hunger Games books, her real name is not revealed. However, you briefly hear her real name, Fleta, in the movies. Fleta is pronounced "Fleh-ta." As Suzanne Collins helped produce the movies and write the script, this can be considered canon. Fleta's last name is unknown, although in fanfiction it oftentimes is Riverwood.
Crash's real name is John Coogan in the book "Crash" by Jerry Spinelli.
In the book "Wringer" by Jerry Spinelli, Beans' real name is Matthew.
Emmett's real mane in the book is Emmett Mcarthy.
squid's real name was Alan.
The real name of Mutto in the book "Wringer" by Jerry Spinelli is George LaFayette.
Tiffany's real name in the book "Wonderland Avenue" is Dawn Schiller.
The author of "The Name of this Book is Secret" is Rafael Frost.
Curly Brannitt's real name in the book "Hoot" is Leroy Branitt.