Pages like NewForm.aspx, NewPost.aspx, etc. do not have the site actions > edit page link, which means you can’t edit the page or add webparts. There is a hack for this.
Workaround 2: The ToolPaneView hack, courtesy of: http://www.cleverworkarounds.com/2008/02/28/more-sharepoint-branding-customisation-using-javascript-part-3/
andyburns said
You can edit those pages in SharePoint Designer. And you can then add web parts. I got an example…
http://www.novolocus.com/2008/09/24/modify-listitem-display-to-show-referencing-items/