The Wikimedia Foundation has set up an offline Wikipedia version themselves understanding this need. The English version with a collection of about 2000 pages can be had in the form of a CD (an ISO file). But it comes at a cost of $13.99.
But here is another solution which is free of charge.A freeware software-
Wikitaxi will helps you.
WikiTaxi enables you to read, search, and browse Wikipedia offline. No Internet connection is needed, all pages are stored in a WikiTaxi database. Because Wikipedia is constantly growing, WikiTaxi uses compression to make sure that the database stays reasonably small. The huge English Wikipedia easily fits on a 8 GB memory stick.WikiTaxi is multilingual,you can use it for Wikipedias from different languages . It also works well with the dictionary and quotation Wikis, if you like. You can also save multiple Wikis to disk and use all of them with WikiTaxi.
Zipedia is a Mozilla Add-on for Firefox enabling offline browsing.
Wikislice is an application that allows the user to collate Wikipedia entries based on a particular topic or subtopic.Wikislice comes as a web based tool as well as a desktop interface. To use Wikislice, just type the topic of your interest in the search bar provided and Wikislice will display all the applicable information for you to browse or download.
A carefully compiled handpicked selection of Wikipedia information and comprises of nearly 24,000 images and 14 million words.