Evolved layouts:

MTGAP's Layout

Michael Capewell's Evolved Layout

Carpalx Layout Optimizer

Peter Klausler's Evolved Layout

Chad Brewbaker's layout

Christopher P. Walker's layout

From colemak.com:

Colemak

Colemak

SorenK's layout a.k.a. OSTNREAI

Seruxie's Layout

DreymaR's layout

Toss the spacebar

The rest:

Workman Layout

Arensito

BvoFrak EN Layout

Amuseum's layout

Maltron Layout

Asset keyboard

DDvorak

Ulf's German Layout

nlite4 Keyboard Layout

Tim Tyler's Layout

Dvorak

Performance Optimization of Virtual Keyboards (research paper)

Slashdot page about alternative layouts

Qwerak

Plum

XPeRT

Rick Harrison's layout

QWERTY