Here's a listing of the top 100 most used fonts from the Fonts.com Web Fonts service for January 2014:

Trade Gothic

Neue Helvetica

Avenir Next

Univers

Avenir

Proxima Nova

Gill Sans

Frutiger

Futura

Helvetica

Linotype Univers

Museo Sans

Museo Slab

DIN Next

Century Gothic

Klint

Bree

Chaparral

Myriad

Rockwell

ITC Avant Garde Gothic

Arial

Univers Next

ITC Caslon No. 224

Eurostile LT

ITC Century

VAG Rounded

ITC Legacy Serif

Neo Sans

ITC Franklin Gothic

Neue Helvetica eText

ITC Lubalin Graph

Gill Sans Infant

Amasis

Optima

Motoya Birch

ITC Legacy Square Serif

Neue Frutiger

Swiss 721

Trade Gothic Next

ITC Officina Serif

ITC Charter

Soho Gothic

Sabon Next

Helvetica World

Frutiger Next

Linotype Sketch

Azbuka

ITC Officina Sans

Lexia

Bodoni LT

PMN Caecilia

ITC Conduit

Linotype Didot

Calibri

ITC Fenice

Bookman Old Style

Humanist 777

Delima

Trade Gothic Next Soft Rounded

Caslon Classico

ITC American Typewriter

Auriol

Monotype News Gothic

ITC American Typewriter Hellenic

Rotis Sans Serif

Adobe Garamond

Soho

Tempo

Bembo

ITC Stone Informal

Droid Sans Mono

Swift

Glypha

Neue Helvetica Arabic

Praxis

Brandon Grotesque

Novecento

Adobe Caslon

Sackers Gothic

Egyptienne F

Perpetua

Francker

Monotype Goudy

Baskerville Classico

ITC Eras

Droid Serif

Serpentine

Orator

Rotis II Sans

C Hei 2 PRC

Clarendon

Bodoni

M Elle PRC

C Hei PRC

M Lady PRC

M Stiff Hei PRC

Comic Strip

Inform

Gibson