Simples... something to charge them with.
The standard way to charge gadgets is a set of individual chargers plugged into a multi-way plug adapter, but often the chargers don't fit next to each other well, and as each takes 'vampire energy' even when not charging (assuming you forget to unplug) you're burning more juice than necessary (estimated at take 10% of residential energy use!). Did you realize that the world currently generates 6.4 megatons of greenhouse gasses purely from smartphone charging? That's equivalent to the emissions from 1.1 million cars.
I just bought the Anker® 40W 5-Port High Speed Desktop USB Charger with PowerIQ™ Technology. It's a tiny block, just larger than a pack of cards (91 x 58 x 26mm), with a single power-cord and 5 USB connectors providing up to 2.4A per port depending on what your device needs (up to a total of 8A). You can plug high load devices into any port and the device will share power appropriately.
The power supply designer did a good job at optimizing idle usage, as stannisu tested it on a kill-a-watt meter reporting that it draws very little current when your devices are fully charged.
It's also great for travel at 235g, supporting 100-240V via a standard figure of 8 power connector on the back (so you can pack just the right cord for your destination country, rather than taking an adaptor).
There's a new version that just turned up in the US if you've got more gadgets, or need even more juice - the 60W / 12A 6-port version. These should filter their way over to the European Amazon sites in the new year (but they won't be here in time for Christmas).
So what are you waiting for?