Walmart, Target, Radio Shack, or Best Buy. I personally would go to Best Buy.
Radio shack is always the best place to buy speakers for any purpose that you want to apply them with and they also have the best sounding ones available also.
The best place to buy radio control parts is Tower Hobbies. You can check out their website here: http://www.towerhobbies.com/ They have a wide selection.
One of the best places to purchase an XM Radio would be Best Buy. Along with the XM Radio itself, one can also find various accessories that may or may not be needed to help it function.
The best place to buy a wireless router would be from your local Best Buy or Radio Shack. There they can give you further information on wireless routers that best suit your needs.
One can purchase a radio controlled clock from a variety of stores or websites. Best Buy would be a good place to look as they carry a large variety of electronic equipment.
Probably the best place to buy an RS232 to USB converter would be Radio Shack followed by Best Buy. A local computer repair shop may also be able to help.
There are many electronic stores and companies that offer car chargers. A few websites that offer car chargers are Radio Shack, Best Buy, TMart and Amazon.
iPod radio clocks can be bought in several places. The easiest places are Best Buy and Target, however they can be found on place like eBay and Amazon.
You can buy at Radio Shack. They have shops everywhere and have really great prices for these wireless modems. You can have them explain how to install it also.
The best place to purchase a CB radio is at www.rightchannelradios.com/best-place-for-CB-equipment. With hundreds of choices and a vast selection, you can't go wrong!
Between Radio Shack and Best Buy, Best Buy has the best digital cameras. They have more varieties and they are never out of stock.