I have actually found that there seems to be more standardization now than before. All of our phones and kindles charge via micro USB cables. Some other random gadgets charge with mini USB cables. Regardless of mini or micro, they all plug into a standard 5V USB outlet.
So I just use this,
http://www.amazon.com/gp/product/B00OHE8AOI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1I leave it plugged into a TT 12V plug. Devices usually come with the mini or micro USB cable, so I just leave one or two plugged into this and hook up devices to the other ends when they need charging.
Moderator edit to re-size picture to forum limit of 640px maximum widhth.