In this age of the "couch generation", you just have to take a front seat in an auction to get yourself wing chairs, sofas, benches, armchairs, dining chairs and stools.
"There are as many forms of seating as conversation," said Philippe Jullian in 1961, in his erudite and amusing little encyclopaedia on "Styles".

Loveseats for tête-à-tête conversations, low chairs for chatting by the fire and sofas for chatting online are all objects you can buy in Seating auctions …

Unless you're looking for a méridienne for a quiet rest, a dos-à-dos (a 19th century double seat placing people back to back) or that psychoanalysis speciality, the couch.
While seating, according to Philippe Jullian, "became lower for romantic reasons and wider to accommodate crinolines" during the Second Empire, the 20th century has its own iconic models, including Harry Bertoia's Side Chair, Charlotte Perriand's chaise longue and Charles Eames' plastic armchair.
Design addicts can sit pretty after an online Seating auction if they garner a sofa by Jean Royère, a chair by Philippe Starck or an armchair by the Bouroullec Brothers.