I combined this and this guide to setup my blog.

# Creating the blog user
useradd blog
passwd blog
usermod -s /bin/bash blog
# Setting up the FTP directory
apt-get update && apt-get upgrade
apt-get install -y vsftpd bindfs
mkdir -p /var/ftp/io.knapen.blog
chown -Rf blog:blog /var/ftp/io.knapen.blog
chmod -Rf 770 /var/ftp/io.knapen.blog
# Setting up the WWW directory
mkdir -p /var/www/io.knapen.blog
chown -Rf www-data:www-data /var/www
# Linking the two together (edit /etc/fstab)
bindfs#/var/www/io.knapen.blog /var/ftp/io.knapen.blog fuse force-user=blog,force-group=blog,create-for-user=www-data,create-for-group=www-data,create-with-perms=0770,chgrp-ignore,chown-ignore,chmod-ignore 0 0
# Mounting the FTP directory
mount /var/ftp/io.knapen.blog
# Setting up the user's home directory
usermod -d /var/ftp/io.knapen.blog blog
# Setting up vsftp (edit /etc/vsftpd.conf)
chroot_local_user=YES
chroot_list_enable=YES
chroot_list_file=/etc/vsftpd.chroot_list
service vsftpd restart