A retractable USB Cable frees us from having to keep a ton of spare USB cables around. This was a freebie we scored at the Bloghaus at CES, but you can find a similar one here. We rarely use our printer, so we like to pull out this cord when we're setting things up temporarily. With the multiple heads, it could let you connect almost any device.
A USB hub solves all problems, and we're lucky enough to have one on the back of our monitor. But, if we ever needed more ports, there are a ton of attractive and useful options out there.
Handsfree chatting is indispensable in our home. If we're on a Skype call, we're on this headset. The Jabra BT250 has never disappointed us, and despite it's goofy form, it's actually quite comfortable.
These are the few things that we can't live without. What's a necessity in your home office?