Is it possible to do an unattended/silent lamp installation?

Yes but you need to create the installation script yourself.

Example that installs Apache 2, PHP 5, MySQL, the Java JDK, NetBeans, and C++. Where PASSWORD needs to be your MySQL password (found that here):

#!/bin/sh

apt-get update
apt-get -y install apache2
apt-get -y install php5 libapache2-mod-php5
/etc/init.d/apache2 restart

echo mysql-server-5.1 mysql-server/root_password password PASSWORD | debconf-set-selections
echo mysql-server-5.1 mysql-server/root_password_again password PASSWORD | debconf-set-selections
apt-get install -y mysql-server

echo '' >/var/www/phpinfo.php
apt-get -y install openjdk-6-jdk openjdk-6-jre
apt-get -y install libnb-platform12-java
apt-get -y install libnb-platform12-java-doc
mget http://download.netbeans.org/netbeans/7.1.2/final/bundles/netbeans-7.1.2\
-ml-linux.sh

#Clean out /tmp...
sudo rm -rf /tmp/*
cd /tmp

#Update this line to reflect newer versions of Netbeans or replace 'javase with 'javaee' or add jee manually via
#Netbeans 'plugins as needed.
wget http://download.netbeans.org/netbeans/7.1.2/final/bundles/netbeans-7.1.2-\

ml-linux.sh
sh /tmp/netbeans-7.1.2-ml-linux.sh --silent

#Add Netbeans launcher to your PATH. Doing so allows you to run 'netbeans' command from the terminal
ln -s /usr/local/netbeans-7.1.2/bin/netbeans /usr/local/bin/

#C++
apt-get -y install build-essential
apt-get -y install synaptic

exit 0

If there is more in this script than you need (like C++, netbeans) just remove the apt-get lines. Also might need to change version numbers to the latest stable versions.