You could also deploy your page layouts as an individual feature rather than creating a whole site definition. That way you could deploy your page layouts to any SharePoint publishing site. If you are using VS 2010, start with a SharePoint Module project. Add your layout aspx file to the project. Modify the elements.xml file to resemble this:
<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
<Module Name="Page Layouts" Url="_catalogs/masterpage" RootWebOnly="True">
<File Path="Page Layouts\Layout1.aspx" Url="Layout1.aspx" Type="GhostableInLibrary" IgnoreIfAlreadyExists="True">
<Property Name="Title" Value="My Layout 1" />
<Property Name="ContentType" Value="$Resources:cmscore,contenttype_pagelayout_name;" />
</File>
</Module>
</Elements>
This deploys your layout and makes it available as for new publishing pages. Now, to get a webpart to be instantiated in new pages, you modify the <File>
element with the webpart definition. For example, I could define a content editor webpart to be created on new pages in Zone1 like this:
<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
<Module Name="Page Layouts" Url="_catalogs/masterpage" RootWebOnly="True">
<File Path="Page Layouts\Layout1.aspx" Url="Layout1.aspx" Type="GhostableInLibrary" IgnoreIfAlreadyExists="True">
<Property Name="Title" Value="My Layout 1" />
<Property Name="ContentType" Value="$Resources:cmscore,contenttype_pagelayout_name;" />
<AllUsersWebPart WebPartZoneID="Zone1" WebPartOrder="1">
<![CDATA[
<WebPart xmlns="http://schemas.microsoft.com/WebPart/v2">
<Assembly>Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c</Assembly>
<TypeName>Microsoft.SharePoint.WebPartPages.ContentEditorWebPart</TypeName>
<Title>Content Editor</Title>
<FrameType>Default</FrameType>
<FrameState>Normal</FrameState>
<Description></Description>
<Height />
<Width />
<AllowRemove>true</AllowRemove>
<AllowZoneChange>true</AllowZoneChange>
<AllowMinimize>true</AllowMinimize>
<AllowConnect>true</AllowConnect>
<AllowEdit>true</AllowEdit>
<AllowHide>true</AllowHide>
<IsVisible>true</IsVisible>
<DetailLink />
<HelpLink />
<HelpMode>Modeless</HelpMode>
<Dir>Default</Dir>
<PartImageSmall />
<MissingAssembly>Cannot import this Web Part.</MissingAssembly>
<PartImageLarge>/_layouts/images/homepage.gif</PartImageLarge>
<IsIncludedFilter />
<ExportControlledProperties>true</ExportControlledProperties>
<ContentLink xmlns="http://schemas.microsoft.com/WebPart/v2/ContentEditor" />
<Content xmlns="http://schemas.microsoft.com/WebPart/v2/ContentEditor">
</Content>
<PartStorage xmlns="http://schemas.microsoft.com/WebPart/v2/ContentEditor" />
</WebPart>
]]>
</AllUsersWebPart>
</File>
</Module>
</Elements>
This should be more practical than creating a whole new site definition. Hope this helps.