The electrical voltage and wall sockets differs throughout the world. For example in most countries in Europe, they use 220 volts at 50 Hertz, rather than the 110 volts at 60 Hertz used in the United States. Additionally, there are several styles of wall sockets, each requiring a different type of plug. There is the 3-Prong version (Used in London) and the 2-Prong (round) version used by others like Italy and France.
You will need plug adapters to fit the different wall sockets and you must check the voltage of your electronic devices to find out whether you need to bring a converter along. Most new devices these days are dual voltage, meaning they are compatible for 110 – 220 volts. This allows you to leave behind that very heavy converter and all you need is to take the plug adapters. This is why I always check the voltage when purchasing any electronic devices (ie, hairdryer, digital camera chargers, etc.)
You can visit most local retailers in your area and find them in the Luggage section. Here is a photo of a plug adapter set I purchased from the REI store.
Tip: If you have multiple electronics to recharge nightly, bring a couple of extra adapter plugs so you can charge multiple items at the same time. I brought two extra plugs on this trip and it was very useful to keep both my IPOD and Camera batteries charged on a regular basis.