Here's a listing of the top 100 most used fonts from the Fonts.com Web Fonts service for November 2013:

Avenir Next

Neue Helvetica

Gill Sans

Trade Gothic

Avenir

Univers

Proxima Nova

Futura

Gill Sans Infant

Frutiger

Helvetica

ITC Franklin Gothic

Rockwell

Linotype Univers

Classical Garamond

Sabon Next

DIN Next

Klint

Century Gothic

Museo Sans

Courier PS

Bree

Chaparral

Myriad

VAG Rounded

ITC Avant Garde Gothic

ITC Caslon No. 224

Eurostile LT

Univers Next

Museo Slab

Neo Sans

Arial

ITC Legacy Serif

Harmonia Sans

ITC Century

Amasis

ITC Lubalin Graph

Neue Helvetica eText

Motoya Birch

Optima

ITC Legacy Square Serif

Slate

Praxis

Neue Frutiger

Trade Gothic Next

Diverda Serif

Swiss 721

Clarendon

Azbuka

ITC Officina Serif

Frutiger Next

Delima

Amadeo

ITC Bodoni Six

Brandon Grotesque

Soho Gothic

Calibri

ITC Charter

ITC Officina Sans

Linotype Didot

ITC Conduit

Helvetica World

Bodoni LT

Chocolate

Adobe Garamond

Lexia

Egyptienne F

ITC American Typewriter Hellenic

Bookman Old Style

Soho

Comic Strip

Swift

ITC American Typewriter

ITC Fenice

Glypha

Droid Sans Mono

Rotis Sans Serif

PMN Caecilia

Auriol

Zapf Humanist 601

Bembo

Monotype News Gothic

Alternate Gothic

ITC Stone Informal

Neue Helvetica Arabic

Francker

VAG Rundschrift

Linotype Sketch

Sackers Gothic

Trade Gothic Next Soft Rounded

Humanist 777

ITC Eras

C Hei 2 PRC

Droid Serif

M Elle PRC

C Hei PRC

M Lady PRC

M Stiff Hei PRC

Monotype Goudy

Caslon Classico