There are two ways to deploy web part pages to a site. one is using the elements.xml to define what is inside the web part zone, like the following.

  
  
             
    <WebPart xmlns="http://schemas.microsoft.com/WebPart/v2"
             xmlns:cewp="http://schemas.microsoft.com/WebPart/v2/ContentEditor">
        <Assembly>Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c</Assembly>
        <TypeName>Microsoft.SharePoint.WebPartPages.ContentEditorWebPart</TypeName>
        <Title>Yet Another Web Part is Born</Title>
        <FrameType>TitleBarOnly</FrameType>
        <cewp:Content>
          This Web Part was added through declarative logic
        </cewp:Content>
    </WebPart>

  
  
  
     
   <WebPart xmlns="http://schemas.microsoft.com/WebPart/v2" 
            xmlns:iwp="http://schemas.microsoft.com/WebPart/v2/Image">
        <Assembly>Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c</Assembly>
        <TypeName>Microsoft.SharePoint.WebPartPages.ImageWebPart</TypeName>
        <FrameType>None</FrameType>
        <Title>Watch My Gears Run</Title>
        <iwp:ImageLink>/_layouts/images/GEARS_AN.GIF</iwp:ImageLink>
   </WebPart>                   

  

Another way is to adding the web parts using code during the feature activating events, like the following.

SPFile page = site.GetFile("SitePages/WebPartPage02.aspx");
SPLimitedWebPartManager mgr = page.GetLimitedWebPartManager(PersonalizationScope.Shared);
// add ContentEditorWebPart to Left Zone
ContentEditorWebPart wp1 = new ContentEditorWebPart();
wp1.Title = "My Most Excellent Title";
wp1.ChromeType = PartChromeType.TitleOnly;
wp1.AllowClose = false;
XmlDocument doc = new XmlDocument();
string ns1 = "http://schemas.microsoft.com/WebPart/v2/ContentEditor";
XmlElement elm = doc.CreateElement("Content", ns1);
elm.InnerText = "This Web Part was added through code";
wp1.Content = elm;
mgr.AddWebPart(wp1, "Left", 0);

// add ImageWebPart Web Part to Right Zone
ImageWebPart wp2 = new ImageWebPart();
wp2.ChromeType = PartChromeType.None;
wp2.ImageLink = @"/_layouts/images/IPVW.GIF";
mgr.AddWebPart(wp2, "Right", 0);