Dynamic DNS, or DDNS, is a type of DNS configuration which allows hosts with dynamic IP addresses to automatically update their DNS records. Often users will rely on services such as DynDNS or No-IP to manage this type of setup, but it is actually relatively easy to run your own DDNS server. Of course, this requires that you have your own domain name and access to at least one host with a static IP (to use as the DNS server).
VPNs allow you to route your Internet traffic through an encrypted tunnel to a remote server, enhancing your privacy while online. Often a VPS is around the same price per month as a dedicated VPN service, but gives you much more freedom and utility as a poweruser. This post will overview a basic routed OpenVPN configuration on an Ubuntu machine.