Seen at Emerald City:

Long Form:
Ian R. MacLeod, The Summer Isles (Aio Publishing)
Sophia McDougall, Romanitas (Orion)
Paul Park, A Princess of Roumania (Tor)

Short Form:
William Barton, “Harvest Moon” (Asimov’s September 2005)
A.M. Dellamonica, “The Illuminated Heretic” (Alternate Generals III, edited by Harry Turtledove, Baen April 2005)
Kim Newman & Paul J. McAuley, “Prix Victor Hugo Script”
Jason Stoddard, “Panacea” (SciFiction, September 14, 2005)
Lois Tilton, “Pericles the Tyrant” (Asimov’s, October-November 2005)

The Sidewise Awards are given for distinguished works of alternate history; this year's winners will be announced at Worldcon (LA Con IV).

Interestingly, the novella version of "The Summer Isles" won the short-form Sidewise back in 1998; I wonder if this will make it two-for-two?