pm-utils provides a bunch of scripts that run on sleep/resume, you could add your script there, but you'll need to be careful as screwing up will likely break resume. Look in
/usr/lib/pm-utils/sleep.d, that's where the scripts are, you can look at the script called
95led as it's quite simple and will be a good model to start with.
95led provides cases for hibernate/suspend and thaw/resume, if you only want resume, you'd write your script like this:
case "$1" in
echo "hey I just got resumed!"
Your script should probably run last, so make sure it shows up last in the directory, maybe name it 99ZZZ_myscript or something. Again, if you're not sure what you're doing here, I wouldn't mess with it. You may end up breaking suspend/resume. If that happens you can delete the script or fix it, but you'll have to do a hard power-cycle to get your system back up.
There may also be a simpler way, but I know this method will work.