I believe it started here: http://benjamin.smedbergs.us/blog/2008-11-24/abc-meme/. Mike provided a speed-up:

C=Components;d=C.classes['@mozilla.org/browser/nav-history-service;1'].getService(C.interfaces.nsPIPlacesDatabase).DBConnection;for(o=[],c=97;c<123;c++){h=String.fromCharCode(c);q=d.createStatement( 'SELECT title t, url u FROM moz_inputhistory JOIN moz_places ON id=place_id WHERE input LIKE "'+h+'%'+'" ORDER BY use_count DESC LIMIT 1'); if(q.step())o.push(['',h,': ',q.row.t,''].join( '' ))}open('data:text/html,'+o.join('\n'))

for FF3.1 - check out minefield and don’t order new hardware just because your browser is slow!

A: http://www.amazon.de/
(it’s Christmas soon)

B: http://musicbrainz.org/
(tag & listen & work)

C: http://cdiac.esd.ornl.gov/trends/emis/em_cont.htm
(a moving target)

D: http://www.deezer.com/
(too many ads)

E: http://exploreourpla.net/
(!)

F: http://feelxfree.blogspot.com/
(Autour de moi les fous)

G: https://mail.google.com/mail/
(unbeatable@G)

H: http://www.intrade.com/jsp/intrade/common/c_cd.jsp?conDetailID=589689
(who knows the future?)

I: http://www.climate-l.org/2008/08/icao-statement.html
(fly but ver)

J: http://www.chrisesler.com/mootools/
(oops - is there an upcoming update?)

K: http://chat.kongregate.com/gamez/0002/7196/live/99bricks.swf
(physical tetris)

L: http://start.ubuntu.com/8.04/
(please - intrepid ibex is running)

M: http://mootools.net/docs/Class/Class
(who said jquery?)

N: http://news.google.com/
(daily update)

0: http://editra.org/
(formats newlisp)

P: http://localhost/info.php
(_.’._)

Q: http://www.brainyquote.com/quotes/keywords/cryosphere.html
(stop the melting!)

R: http://www.hittail.com/login.asp?c=0
(traffic, traffic, traffic)

S: http://blog.songbirdnest.com/
(itunes? - pfffh)

T: http://www.mousegestures.org/forum/viewtopic.php?id=147
(installed easystroke instead)

U: http://data.un.org/Default.aspx
(emissions per inhabitant per kilowatt per year per country)

V: http://www.green.tv/
(greenTube)

W: http://www.ehrensenf.de/shows/ehrensenf/wachskunst-stadtzeichner-falsche-hand
(Jeannine rocks)

X: http://feeds.feedburner.com/transportenvironment/bulletin?format=xml
(transforms transport)

Y: http://mlt0.google.com/mapslt?lyrs=lmc:panoramio,lmc:wikipedia_en&x=1316&y=3176&z=13&w=256&h=256&source=maps_
(google knows to render)

Z: http://www.zeit.de
(german, best value / text and money )

Just type letter by letter in the location bar of your browser and blog the first result from the proposals.