A project on CodePlex adding a lot of value for SharePoint projects is the "SharePoint 2007 features" project. It has grown considerable during it lifetime and it is absolutly worthwhile checking back from time to time.
As a developer you might specially apreaciate the "Debugger feature". It adds a link to your site actions menu:
Mark Arend has an article about "Debugging web parts and other SharePoint custom code" with some more information about this feature.