While working on a Drupal Commerce project for a client, which will be handling products and donations will also need to handle conference registrations. There is a commerce_registration module which is looking like a very nice contribution and should work well. The commerce registration module adds a new page to the checkout process for the custom registration fields that are mapped for the selected item being purchased.
I'm working on another SQL Server 2008 and Drupal 7 project right now. This particular project has a great deal of stored procedures and triggers in it to massage extrenal data to the right format for display in Drupal.
Doing Drupal/PHP development with SQL Server 2008 is easy using the 2008 Express (free) edition for those of us who don't use SQL Server regularily as a database on our development machines. However, there is one small problem I ran in to on this current project: SQL 2008 Express does not have any UI mechanisms in the SQL Management Studio to allow you to manage triggers!