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

Neue Helvetica

Trade Gothic

Avenir Next

Univers

Avenir

Proxima Nova

Frutiger

Gill Sans

Futura

DIN Next

Helvetica

Linotype Univers

Museo Sans

Museo Slab

Century Gothic

ITC Avant Garde Gothic

Klint

Chaparral

Arial

ITC Lubalin Graph

Eurostile LT

Rockwell

Azbuka

Myriad

ITC Legacy Serif

Soho Gothic

ITC Caslon No. 224

Neo Sans

VAG Rounded

ITC Century

Univers Next

Motoya Birch

Optima

ITC Franklin Gothic

ITC Legacy Square Serif

Aachen

Linotype Sketch

Neue Frutiger

Trade Gothic Next

Swiss 721

Gill Sans Infant

ITC Charter

Frutiger Next

Neue Helvetica eText

Swift

Bookman Old Style

Bodoni LT

ITC Officina Serif

Lexia

ITC Officina Sans

ITC Eras

Calibri

Humanist 777

Adobe Garamond

Auriol

PMN Caecilia

Linotype Didot

ITC Conduit

Trade Gothic Next Soft Rounded

Soho

Helvetica World

Rotis Sans Serif

Minion

ITC Stone Informal

ITC American Typewriter Hellenic

Georgia Pro

Bembo

ITC American Typewriter

Brandon Grotesque

Droid Sans Mono

Akko

Egyptienne F

C Hei 2 PRC

ITC Fenice

Eurostile Next

M Elle PRC

C Hei PRC

M Lady PRC

Slate

M Stiff Hei PRC

Monotype News Gothic

Droid Serif

Monotype Goudy

Novecento

Baskerville Classico

Adobe Caslon

Orator

Delima

Neuzeit Office Soft Rounded

Caslon Classico

Copperplate Gothic

Glypha

Francker

Twentieth Century

Bodoni

Rotis II Sans

Comic Strip

Droid Sans

Perpetua

Sackers Gothic