How to implement “Cancel” functionality in a VisualForce Page

Apex Class:

public class sampleExtension {

  ApexPages.standardController std = null;

  public sampleExtension(ApexPages.standardController sc)  {

    std = sc;

  }

  public PageReference doCancel()  {

    return std.cancel();

  }

}

VisualForce Page:

<apex:commandButton action="{!doCancel}" value="Cancel"/>

Note: this doesn't necessarily take you to the list view, it'll return you to the last page you were viewing before going to the VF page.

Reference: 

http://www.salesforce.com/us/developer/docs/pages/Content/apex_pages_standardcontroller.htm