MOSS: XmlFormView Control
Here is a nice article about using an XmlFormView Control
A browser-enabled InfoPath form template is functionally equivalent to a form designed to run in Microsoft Office InfoPath 2007, but when it is published to and opened from a server running InfoPath Forms Services, it does not require Office InfoPath 2007 to be installed on the computer that uses the form. InfoPath Forms Services, as part of either Microsoft Office Forms Server 2007 or Microsoft Office SharePoint Server 2007, includes the XmlFormView ASP.NET control, which you can use to render a browser-enabled form in a custom Web page. The XmlFormView control benefits enterprises that want to incorporate the functionality of InfoPath forms into their organizational Web infrastructure.
MSDN Article: Hosting the InfoPath 2007 Form Editing Environment in a Custom Web Form