In view of the 9/11 attacks, with some fighters being launched unarmed
for want of time, I have been wondering what are the procedures to be
followed before launching fighters onto a mission--I am not talking
about authorizations etc., but things like fueling them (or are they
kept fueled?), loading missiles (special operation to arm them?),
briefing the pilots (and the aircraft's computers?)...

In the old days aircraft were sitting on the ramp fully fueled and armed
24/7 with their pilots never more than a few minutes away.
They could be in the air in under 5 minutes from the alarm being given (and
during times of increased tension in under 1 minute, aircraft under those
conditions being kept on standby with pilots in their cockpits and engines
running (with fuel lines connected to keep the tanks topped off).
Since about 1993 that has been generally reduced so that now the average
reaction time is 45 minutes.
Aircraft are unarmed, pilots are further away from them, etc.

I thought Google would give me a list, but I apparently didn't find
the right keywords. What are the standard procedures and checklists
before taking off? Are they different from training missions? From
flights with civilian aircraft?

Checklists would be abbreviated, or rather the checks would largely have
been performed beforehand by the groundcrew while the pilot was on his way
to the aircraft.