Cleat Types
SPD Cleats

SPD stands for Shimano Pedal Dynamics. These cleats have a 2-bolt pattern which is typically found on mountain style pedals and spin bikes.
SPD-SL

SPD-SL stands for Shimano Pedal Dynamics Super Lightweight. These cleats have a 3-bolt pattern and are typically found on road pedals.
Crank Brothers

Crank Brothers cleats have a 2-bolt pattern and are only compatible with Crank Brothers pedals.
Campagnolo Pro Fit

Campagnolo cleats have a 3-bolt pattern and are only compatible with Campagnolo pedals.
Look KeO

KeO cleats have a 3-bolt pattern and are compatible with Look KeO pedals.
Look S-Track

S-Track cleats have a 2-bolt pattern and are only compatible with Look S-Track pedals.
Time ATAC

ATAC cleats have a 2-bolt pattern and are only compatible with Time ATAC pedals.
Time Iclic

Iclic cleats have a 3-bolt pattern and are compatible with Time Iclic, Iclic 2, and Xpresso pedals.
Time RXS

RXS cleats have a 3-bolt pattern and are only compatible with Time RXS pedals.
Xpedo XPT
XPT cleats are found on M-force and a few other Xpedo models. They are a two hole cleat.
Xpedo Thrust 7
The Thrust 7 are a three hole cleat, found on the Thrust pedal models.