I wanted to buy a DC (car) charger for my Microsoft ZUNE media player, but the only ones I can find, in retail stores, also include an FM transmitter, and they run from the upper thirties to the lower fifties, in dollars. Instead, I went to Wal*Mart and bought a DC Y-Adapter plug that also includes a USB port. So now, I can charge (or run) any USB device, assuming I have the device's USB cable with me. It's a cheaper solution, than buying a proprietary charger designed for just one species of device, and you get to charge any device you wish.
They also make Inverters of about the same size, but I already have an inverter and I didn't want to double-up. Besides, the Y-Adaptor is convenient anyway, as I can run my GPS, charge my cell phone, and power my Zune all via the one device.
The price: $9.99.
Ø An Inverter changes DC power over to AC power, providing a standard "wall outlet(s)" for one's AC device(s). Inverters are rated in Watts, which directly relate to how many gizmos you can power with a given Inverter. A 140-watt model, with one wall outlet and one USB port can be seen here (assuming the link has not retired as you read this from the future). Most such devices list the sorts of devices you can power with them, and mostly, they are honest about it. Me, I just do the math: Look on your devices (or their manuals), for how many Watts (or if you're lucky, peak-Watts) they use. Add up all the Watts you'll need, and buy your inverter accordingly, rounding up enough for wiggle room. Example: You add up your needs and you find that your devices, in the aggregate, should use 148 Watts. Don't buy a 150 W inverter, in that scenario. Instead, buy a 200 W unit. Wiggle room.
Ø I didn't want an FM transmitter because I haven't had good luck with them, in my car, so I instead use a cassette adaptor; my car stereo has both CD and cassette, and I'll certainly never put a cassette in there, so I might as well use it as a port for my media devices.
Ø My ZUNE's "Travel Kit" came with an extra USB cable, so I readily have one with me, which means I do not have to take the one, off my PC, that I use for syncing. Oddly, the travel kit did not come with a DC adaptor…but it did come with an AC adaptor. This makes it nice for getting somewhere, not traveling to one's destination. Thus I think they should rename it "ZUNE Destination Kit".