JavaTuner with some extra "custom" temperaments. Save this HTML page on your system to add your own.

Custom temperaments/tunings (to load, type the uppercase key in the applet):
Key Temperament/tuning Notes
D Mean semitone
F French
G Grammateus
I Irregular French 17th
L Lucy's temperament See comments
N Neidhardt 1932 Village [thanks to Johan Norrback]
M Marpurg
R Rameau
T French (2) As per Lindsay's article in EM [thanks to John Wood]

Pending work: sort out the Neidhardts (I know of at least eight: which is most typical -- I get conflicting infos)