Evolved layouts:

MTGAP's Layout
Michael Capewell's Evolved Layout
Carpalx Layout Optimizer
Peter Klausler's Evolved Layout (dead link)
Optimized 1-Finger Layout
Chad Brewbaker's layout
Christopher P. Walker's layout
Keyboard Layout Optimizer – Travis Brown (incomplete)

From colemak.com:

Colemak
nawfal's layout
BvoFrak EN Layout
SorenK's layout a.k.a. OSTNREAI
Seruxie's Layout
DreymaR's layout
Toss the spacebar

The rest:

Workman Layout
Arensito
Amuseum's layout
Maltron Layout
Asset keyboard
Neo (German)
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
qwpr
XPeRT
Rick Harrison's layout (dead link)
QWERTY