European electrical voltage and plug adapters

For most phones and laptops you do not need to worry about the European standard 220 Volts since manufactures of travel appliances (razors, hair dryers, cell phones, etc) have designed the chargers and power adapters to handle a range of power from 100 Volts to 240 Volts (for North America, 110 Volt is standard) and convert it to whatevever output your appliance requires to run or charge it.
You will however, need to have a PLUG ADAPTER in order for your US plug or charger to fit in the wall in any standard socket in Europe.  These adapter plugs are readily available online for a few dollars or at Radio Shack, Best Buy and even Walmart sometimes in a kit with more plugs than you need.  I recommend EBay where I recently bought 20 plug adapters for $10 and passed them out to the board and staff.  The plug adapter is a must have item if you plan to have a phone, tablet or laptop charged while in Europe.  The picture above shows the configuratiuon of the European standard wall plug with the flip side showing the standard US wall plug.
All rooms at the convention hotel in Tallinn have hair dryers in the room and irons available.