Rozetka.ua is one of the most popular Internet services in Ukraine, where the user can buy a lot of different electronic appliances. They have their own delivery service,and if consumer buys something it will be delivered in 1-2 days, depending on when you've made a request for buying something.. Prepayment is not required. A lot of my friends have already used it and nobody had any troubles or  misunderstandings. Rozetka works perfectcly. All goods are of a good quality and value for money.

 Here is some interesting information about e-commerce in general.

Here you can see more about history of e-commerce and comments of people, who have business on the Internet.

Qiwi is a payment service, that is used for paying for diferrent everyday services such as mobile communication and housing services, bank loans etc.This service provides either payments in cash and payments on the Internet . Qiwi works in 15 different countries, including Russia, Ukraine, Kazakstan, Moldova, Byelorussia, Tadzhikistan, Rumania, China, Panama, Malaysia, Argentina, India, Kirghizia, Serbia, Latvia and Republic of South Africa.The user must create and register his account in "Qiwi-Wallet", to pay for services on the Internet.

WebMoney is an electronic money and online payment system (transactions are conducted through WebMoney Transfer). WM Transfer Ltd, the owner and administrator of WebMoney Transfer Online Payment System, was founded in 1998 and is a legal corporate entity of Belize, Central America. Every account, known as a "purse", is run in Gold-equivalents (WMG), US Dollar-equivalents (WMZ), ruble-equivalents (WMR), Belarusian ruble-equivalents [WMB] euro-equivalents (WME) or hryvnia-equivalents (WMU). From May 31, 2011 system supports Vietnamese đồng-equivalents (WMV), but only through a mobile phone interface.Also, Kyrgyzstani som and Uzbekistani som-equivalents (WMS) and (WMY) were expluatated, but canceled by central system authority.Accounts are identified by strings called WM-IDs; account holders can remain completely anonymous towards each other.Signing up and receiving webmoney (known as "WM units") from other users is free; sending WM units to other accounts incurs a fee of 0.8%. Funds can be deposited into or withdrawn from webmoney accounts by money order, wire transfer, by conversion from other electronic currencies, or by cash transactions at authorized exchange offices; all of these incur various fees. It is also possible to purchase WM cards for $10–$100 in order to fund an account.

Electronic commerce, commonly known as e-commerce, ecommerce, eCommerce or e-comm, refers to the buying and selling of products or services over electronic systems such as the Internet and other computer networks. Electronic commerce draws on such technologies as electronic funds transfer,supply chain management, Internet marketing, online transaction processing, electronic data interchange(EDI), inventory management systems, and automated data collection systems.