First things first: IF (and that's IF) you get the genuine OEM Motorola charger listed here, the SPN5400, it works great with modern smart phones like the Motorola Droid, The Incredible, The Google Nexus One, etc. Basically, if your phone has a micro USB connector (and almost all of the newer generation smart phones do), then this is the charger for you.
That said: Not every seller is selling the right item. There are lots of reports of people getting the wrong charger (I've had this happen myself). Your best bet: Amazon, who not only IS selling the correct charger, but has the best price, when you factor in shipping, provided you qualify for free shipping from Amazon (either with Prime, or if your order is > $25).
The Amazon listing for this charger can be found here: Motorola P513 Vehicle Power Adapter MicroUSB Rapid Rate Charger. Search through the sellers to find Amazon. Their price, if you get free shipping from Amazon, is the cheapest. And you are guaranteed of getting the correct item, brand new, retail.
OK, that said, here's the rest of my review:
There are so many sketchy sellers selling phone chargers out there, that it can be a bit scary. The problem is that if the charger is poorly made, the output of the charger can be out of spec and can, in some cases, fry the phone you connect to it.
For that reason, when it comes to phone chargers, you should stick to name brands. (They are all made in China, but the name brand ones are usually subject to stricter QA).
When I found this charger on Amazon, SOLD BY AMAZON, I jumped on it. It's a MICRO USB car charger, made for Motorola and sold under the Motorola name, in retail packaging. The rated output is 4.75-5.25V and 950mA.
This charger should work fine with most any phone that uses the MICRO USB connector. The key number to pay attention to is the second one, the rated amperage. This is the MAXIMUM amount of current that the phone can request from the charger. A typical USB port on a PC provides as little as 100mA, and few provide more than 500mA. So this charger should charge your phone faster than when it's connected to a PC. A few phones out now can use up to 1000mA. But that just means they CAN use that amount. If 950mA is provided, they'll still charge, just a bit more slowly.
Note that the amperage (second number) merely tells you how much the charger CAN supply, if requested. The phone itself is responsible for asking for the current. That is to say, if this charger can provide 950mA, but your phone can only use 300mA--no problem. Your phone asks for 300mA and the charger provides all of what is requested. If, on the other hand, your phone can use 1000mA, this charger will provide all it can, which is 950mA--a wee bit less than the max asked for. That's also not a problem; it just means your phone will charge a little bit (not much in this case) more slowly. The rated voltage for this charger is presented in a range of 4.75-5.25V. The "ideal" voltage for a USB charger of any type if 5V. And most chargers for home use are rated right at 5V. But car chargers work in a noisier environment and thus you have the range. This is where a cheapo charger can really do damage, as some of them are poorly regulated and can provide voltages that are WAY out of spec. Again, when you can get a name brand charger from a seller you can trust (Amazon) for such a reasonable price, it's very foolish to consider the cheapo no-names.
This is an excellent quality name brand travel micro USB charger at a price that beats the no-name junk from third party sellers. What's not to like?
BE SURE TO ORDER IT FROM AMAZON AND NOT ONE OF THE THIRD PARTY SELLERS, as some of those have been known to make mistakes with respect to what they ship relative to the listing. I can confirm that Amazon is shipping the P513 /89143N /SPN5400 charger, as pictured.