Run these commands in your console, they will edit necessary files:

echo 'basename "$VIRTUAL_ENV" > ~/.last_venv' >> $VIRTUALENVWRAPPER_HOOK_DIR/postactivate
echo 'rm ~/.last_venv' >> $VIRTUALENVWRAPPER_HOOK_DIR/postdeactivate

Then open your ~/.bashrc or ~/.profile or whatever your shell uses and append:

if [ -e ~/.last_venv ]; then
    workon `cat ~/.last_venv`
fi