Can any body provide me useful links by which i able to integrate mail chimp with shopping cart checkout page so that every user passes by checkout page added to mail chimp list to get newsletter.
Checkout MailchipAPI there you can create list and add users to it with the help of pre defined functions.
In mailchimp you can divide a list into a number of groups so you can filter your users as per your needs. http://apidocs.mailchimp.com/api/1.1/listinterestgroupadd.func.php
then you can add users to the list. http://apidocs.mailchimp.com/api/1.3/listsubscribe.func.php
then you can create campaign to send mail to specific group http:// apidocs.mailchimp.com/api/1.3/campaignsendnow.func.php