Here's a ranked listing of Fonts.com Web Fonts' top 100 most used Web fonts for December 2011:

Futura® Bold

Neue Helvetica® 55 Roman

Neue Helvetica® 35 Thin

Neue Helvetica® 75 Bold

Neue Helvetica® 45 Light

Univers® 57 Condensed

Avenir® 85 Heavy

Futura® Bold Condensed Oblique

Garamond 3 Regular

Garamond 3 Italic

Bauer Bodoni® Black Italic

Avenir® 35 Light

DIN 1451 Engschrift

Sackers™ Gothic Heavy

Sackers™ Gothic Medium

Trade Gothic® Bold

Avenir® 65 Medium

Helvetica® Condensed Bold

Linotype Univers® 620 Condensed Bold

Neue Helvetica® 25 Ultra Light

Futura® Medium

Trade Gothic® Condensed Bold 20

Avenir® 95 Black

Linotype Univers® 420 Condensed

Linotype Didot® Roman

Linotype Didot® Bold

Avenir® 55 Roman

Neue Helvetica® 65 Medium

Univers® 47 Condensed Light Oblique, Extended

DIN Next™ Condensed Bold

Linotype Univers® 320 Condensed Light, Extended

Futura® Book

Linotype Didot® Italic

Neue Helvetica® 67 Condensed Medium

Neue Helvetica® 77 Condensed Bold

Trade Gothic® Roman

Laurentian™ Semi Bold Italic

Neue Helvetica® 63 Extended Medium

DIN Next™ Bold

Trade Gothic® Bold 2

Futura® Bold Condensed

Avenir® 45 Book

Futura® Medium Condensed

Neue Helvetica® 53 Extended, Extended

Neue Helvetica® 73 Extended Bold, Extended

Trade Gothic® Condensed 18

Futura® Heavy

PMN Caecilia® 85 Heavy

PMN Caecilia® 75 Bold

ITC Avant Garde Gothic® Book

Neue Helvetica® 57 Condensed

Trade Gothic® Condensed Bold #20, Extended

Neue Frutiger® Book

Neue Frutiger® Bold

PMN Caecilia® 76 Bold Italic

Neue Helvetica® 47 Condensed Light

DIN Next™ Regular

Neue Helvetica® 45 Light, Extended

Neue Frutiger® Light

VAG Rounded™ Bold

Monotype Grotesque® Condensed

Helvetica® Bold

DIN Next™ Condensed Regular, Extended

Neue Helvetica® 55 Roman, Extended

Trade Gothic® Bold, Extended

Neue Helvetica® 37 Condensed Thin

Trade Gothic® Next Regular

Futura® Book, Extended

Univers® 67 Condensed Bold Oblique

Helvetica® Bold, Extended

Avenir® 55 Roman, Extended

Rockwell® Bold

ITC Avant Garde Gothic® Medium

Trade Gothic® Extended Bold

VAG Rounded™ Light

Futura® Bold, Extended

Trade Gothic® Condensed #18, Extended

Neue Helvetica® 65 Medium, Extended

Felbridge™ Regular

Neue Helvetica® 46 Light Italic

Figural™ Book

Frutiger® 65 Bold

Neue Frutiger® Regular

Univers® 55 Roman

Baskerville Regular, Extended

Helvetica® Bold Italic

VAG Rounded™ Black

ITC Avant Garde Gothic® Bold

Gill Sans® Book

Neue Frutiger® Bold Italic

Frutiger® 45 Light

Univers® 45 Light

Frutiger® 45 Light, Extended

Avenir® Next Demi

Eurostile® LT Bold

Frutiger® 65 Bold, Extended

Neuzeit® Office Bold

Eurostile® LT Roman

Neuzeit® Office Regular, Extended

Trade Gothic® Bold #2, Extended