A script this time for all of y'all.  :)
Assumes: you have Photoshop CS3, a Style saved called 'Black' which is a layer blend, color overlay, black #000000 at 100% opacity.  (make this, duh)
Also assumes: you have a folder full of sequentially numbered png images with a prefix such as: 'a001.png', 'a002.png', 'a003.png'
Lastly assumes that you want to give 100% black opacity to the first, 50% to the second, and 0% to the third (or if you have 100 files, decreasing amounts of 1% opacity to each until you get to 0%).

Save the below as a .jsx file.  Known error: odd/even numbers of files will yield opacity <0, giving an error right at the end.  Round doesn't fix it.  It's not a game killer, so I don't care at this point, honestly.
Other issue: LJ must hate semicolons.  Security issue?  Perhaps.  Put one at the end of each line except for the first, the one ending with { and the one ending with }


Then File >> Scripts >> Browse and sit back and enjoy.  :)
 

#target photoshop
app.bringToFront()

var filePrefix = "css"
var fileExtension = ".png"
var firstNum = 342
var lastNum = 380
var currentNum = 0

fileObj = new File()

var inputFolder = Folder.selectDialog("Select a folder of images to process")

filePrefix = prompt("file prefix, but not the number or extension. such as: a or css or dsc")
fileExtension = prompt("file extension including dot such as .png")
firstNum = prompt("first file number such as 001")
lastNum = prompt("last file number such as 999")

currentNum = firstNum

var fileRef = File(inputFolder+"/"+filePrefix+currentNum+fileExtension)
alert (fileRef)
var docRef = app.open(fileRef)

pngSaveOptions = new PNGSaveOptions()
pngSaveOptions.interlaced = false

while (currentNum < lastNum+1) {
 
 docRef.backgroundLayer.copy()
 docRef.paste()
 docRef.activeLayer.applyStyle ("Black")
 docRef.activeLayer.opacity = (100*(((lastNum-currentNum)/(lastNum-firstNum))))
 docRef.flatten()
 docRef.save(pngSaveOptions)
 docRef.close()
 
 currentNum++
 fileRef = File(inputFolder+"/"+filePrefix+currentNum+fileExtension)
 docRef = app.open(fileRef)

}

docRef.close()
alert ("Done")


......

I had trouble finding a way to do this via many many google searches.  I found a tutorial on stitching images into a panorama, and sort of extrapolated from there.  On the off chance that someone else has a unique need to batch job 100+ files in a folder and turn them from:
X   into

XX
XX

this is the droplet/script for you!  :)
http://www.megaupload.com/?d=Y6WUU1IR

Brief tutorial on droplets: download droplet to desktop (or anywhere), open folder with files to modify, select files and drag/drop them onto the droplet icon where you saved it (desktop of whatever).  Will open photoshop and batch run them all.  Kick butt. 

This droplet (exe) is clean and safe, but feel free to run it thru ur Norton or AVG or whatever first.  Lord knows I would.  :)
Enjoy!

Okay, two things:
Number one, multiplayer on the new 24" Playstation screen with no. more. split. screen!!!  *nosebleed* (not crazy about the $499 price, but I spoze it's a good deal for what you get...)
Number two, I want this 72 foot screen in ma house so bad!!!  LOL  @_@