Even though they've been providing the same great service for ten years, I had never used DynDNS before (ah, the joys of working from home and having a dynamic IP that stays fairly stable), but I just signed up and it's sweet. Just register a subdomain at DynDNS.com for free, which will then map itself to your dynamic external IP address automatically in one of two ways: by logging into your DynDNS account on a router that supports it (many do) or downloading a free update client for your computer that can also keep everything synced.
Then you don't have to remember a nasty number when you want to access your network from an external computer. Nice!
Please keep the constructive comments coming in our Saturday How To guides—they're a great resource for everyone involved. Also thanks to twonjosh for sharing his method of dealing with dynamic IPs. [DynDNS]