I recently completed an asp.net application that shows how to integrate with two leading online payment service providers, PayPal and Google Checkout. It is based on the classified app from the asp.net starter kit. Development tools and technologies include: VS 2008, ASP.NET 3.5 and LINQ.
The current release includes basic functions of collecting data from users or customers, the process of converting a quote to a sale order and email notification. Future releases will include features such as improved user interface, exporting data to Excel files, and asynchronous email notification.
You can download the application at Microsoft codeplex, http://ezquoder.codeplex.com/
If you would like to add a photo gallery feature to the application, you may find this Silverlight application useful. It is available for download at http://photogallerywallcs.codeplex.com/ A more sophisticated Silverlight application "SlideShow" created by Vertigo is available at http://www.codeplex.com/SlideShow