There seems to be a lot of incomplete tutorials out there relative to installation and configuration of Ant on Ubuntu. Here is how to do it correctly.
Open .bashrc and add the following lines
#Setting some paths
export ANT_HOME=$HOME/tools/apache-ant-1.8.1
export JAVA_HOME=/usr/lib/jvm/java-6-sun
# Add stuff to the path and export it in one step
export PATH=$PATH:$ANT_HOME/bin:$JAVA_HOME
Prerequisites: download ant and expant that into a folder (I use $HOME/tools) for all my tools.
rohit@lenovo:~$ ant -version
Apache Ant version 1.8.1 compiled on April 30 2010
Done.