If my memory is correct, someone on this list was looking
to drive an LED with less than the LED's forward voltage.
(If that's wrong, my appologies for boring the list with this.)

If I remember aright, several folk recomended the LM3909,
but it wasn't bright enough?

http://209.1.238.250/arpdf/AppNotes/A1913.pdf
shows how to use a MAX778 to drive High Brightness LED's
from a 1.5 volt source.
(This should be bright enough for almost anyone.)