June 2008.  This is a simple listing of "Britannia-like" games, both published and being worked on, that I know of. See also Rick Heli's list, which includes games that I would call "sweep of history" but not Britannia-like.

Roughly defined, Britannia-like games use many of the game mechanisms of Britannia, as well as the idea of multiple nations seeking varied point goals, controlled by one player, playing independently.

Ancient Conquest (1975, Excalibre Games) originated the idea of multiple nations controlled by one player but seeking varied point goals, yet otherwise bears so little similarity to Britannia that I do not consider it "Britannia-like". I read the rules for AC once while watching a game played, then did not see it again until I bought a used copy in 2005.

Ancient Conquest II (1978, Excalibre Games). I have not seen this game.

China: The Middle Kingdom (Decision Games, July 2008) covering the entire history of China to the modern day, an old-school Britannia-like game.  The full game has something like 45 nations, 24 turns, 40-some areas on the board, 300-some pieces.  (I'm saying "some" because I have not received my copy, saw one at Origins.)

Italia (Phalanx) 2007, by the author of Hispania, over 500 pieces, separate three player version and four player version; nominated for Origins award

Hegemonia (Greece from Iliad to destruction of Corinth by Romans). Self-published 2004 (City-of-Games), rules presently in German only.

Britannia Second Edition (FantasyFlightGames, 2006, reprint and international edition forthcoming August 2008)

Britannia (1986 H. P. Gibsons, UK; 1987 Avalon Hill, USA; 1991 Welt der Spiele, Germany (German language)); nominated for Origins award

Peninsula Italica (Camelot, 1993). I have heard that this is a poor game, but have not seen it. IIRC it covers Rome's rise rather than later Italian history. May be in Italian language.

Maharajah (1994, Avalon Hill; French version by Eurogames / Descartes).

Hispania (1994 Azure Wish, France). 640 pieces!

Chariot Lords (1999 Clash of Arms). This is about as far as I would go in defining "Britannia-like"

Rus (2000, Desktop Published, Simulations Workshop)

The Dragon & The Pearl (2004, Spirit Games UK)

Mediterranea. "Published" on the Web, not for sale. URL: http://www.geocities.com/davidbofinger/darkness.htm

Of these only Britannia, Italia, Hegemonia, China, and Chariot Lords can be purchased brand new.

Complete but not (yet) published:

Roger Heyworth (uncredited developer on Gibsons version of Britannia) designed Conquest Europa, a very large unpublished game (he is, unfortunately, deceased), information at Boardgamegeek.

Eurannia by Ralf van der Post, Scythians to 18th century, about 12 hours, 1995.

Britain: Torben Mogensen (Albion, appears to be complete)

Britain: Arthuria:Adventus Saxonum --Britons vs. "Saxons" in England and Wales

Britain: Lew Pulsipher   This is a "Gateway" version of Britannia, 8 nations, 6 turns, 90 minutes.  Alpha testing.  Likely to be given away at some point as an introduction to Brit.  Posted at Eurobrit Yahoo Group.

Byzantium: Simon Bullock

Byzantium: Lew Pulsipher (not even alpha)

China: Lew Pulsipher, small scale, two scenarios, alpha testing

Europe as a whole: Lew Pulsipher (Barbaria, several versions, in early beta playtesting)

Fantasy: Torben Mogensen (Hy Breasil, appears to be complete)

Frankia: the Early History of France and Germany: Lew Pulsipher, diceless (card-based combat), beta testing

Iberia: Lew Pulsipher, in alpha testing; much simpler and smaller than Hispania

India: Lew Pulsipher, alpha testing, small scale with two scenarios (early one for three players)

Italy: David Bofinger (alpha test)

Normannia (Viking history): Lew Pulsipher, close to beta, two versions

Romania: Torben Mogensen

Russia: Lew Pulsipher (alpha)

Scotland: Lew Pulsipher (Caledonia in early beta playtesting)

South American Britannia: Simon Bullock.  Starts with conquistadors, ends with Spanish being kicked out (alpha)

Wales: Lew Pulsipher (Gwallia Cymru, not yet alpha)

I have designed three "expansion" versions of Britannia (Epic (add Ireland, more detail), Brevis (10 turns, diceless), and Minimus (6 turns)), but Fantasy Flight is not currently interested in publishing an expansion.

I have not listed variants of games, such as those designed by the "Black Prussian". A list of variants would be a nice addition, if someone would care to put it together.

"A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away."  Antoine de Saint-Exup'ery