Thanks. For those who may be interested, here are a couple tools I ended up using:
I did my find (redirected to a temporary file) and got the list of file names that looks something like this: aarode_2007-08-14_16-56-41.041_1258.upload.lsx.gz
Then I used this code to get just the last name (the part up to the first "_"):
for file in `cat /tmp/list.$$`; do
NAME=${file/_*/} # this substitutes nothing for everything after the first _
...
done
Then I used this piece to get the first letter
FIRST=`perl -e "print substr($NAME,0,1)"`
Doesn't feel pretty but it works.