Ted is absolutely right.
Motivation [IF you want it to stand for a long period] HAS......repeat HAS......to come from within. Any amount of extraneous efforts will only give you short-term results [if that's your intent, then it's OK].
Suggest create conditions where they become a 'part of the solution' than being a part of the problem......from YOUR perspective, that's what they are right now.
Like Stevan mentioned, you need to be BRUTALLY honest with them....about where things stand, what are you doing about it, what's YOUR prognosis, etc.
I have seen situations where the lowest guy in the ladder can come-up with such gems of advice that you MAY end-up feeling 'why didn't this occur to me in the first place'.
Quite often, many crucial aspects of a situation MISS the ones closest to the scene handling it [sort of nearsightedness where one can't see the other aspects of the situation] that the others in the team CAN SEE.
And the added advantage....from a management perspective.....of involving the team in this is that you create a 'sense of belonging'--something that CAN'T be done in any other way. One doesn't share & ask for advice from 'outsiders' in critical situations......right?
That's what I guess Ted meant when he says 'added benefit of showing that you respect their opinions and are actively listening to them'.
However, after such an interaction, sometimes there COULD be people who might think 'this is too much for me to handle', for whatever reasons, and MAY want to quit. Suggest DON'T STOP them, unless he/she is too valuable for the Company--in which case, you would need to find other ways to hold them.
As far as appreciation & celebration goes, look for ways that don't take a lot of money.....there are many ways to do it without blowing a hole in your pocket. One way I found very effective has been to RECOGNIZE THE EFFORT PUBLICLY, with outsiders if you can.
For eg, introduce the guy responsible, let's say for some critical S/W, to the end-user/outsider/client: Hey! he's the guy who did it. That works wonders to pep-up the motivation levels without spending a dime. [this also inculcates a healthy competition within the team....but that's not your focus now].
In case you are looking for very specific situations to be handled, suggest post the details here.....I am sure the members of this Forum will be able to give you very actionable suggestions.
All the Best.