Looking at my older post http://www.decatec.it/blogs/2007/11/14/Sharepoint+MOSS+NET+Platform+Review.aspx it reminded me Sharepoint IS .NET and ASP.NET based, therefore (almost) anything is possible via code ....

Some post about Sharepoint + .NET
http://weblogs.asp.net/scottgu/archive/2006/04/30/SharePoint-2007-_2D002D00_-Built-on-ASP.NET-2.0-.aspx
http://vspug.com/jessefitz/2008/01/24/integrating-an-asp-net-application-into-our-sharepoint-portal/
understanding asp.net + Sharepoint
http://www.intranetjournal.com/articles/200708/ij_08_24_07a.html

Which one to use Sharepoint or ASP.NET?

http://blogs.msdn.com/sanjaynarang/archive/2009/06/19/should-i-build-my-application-in-sharepoint-vs-asp-net.aspx

http://blogs.msdn.com/cjohnson/archive/2007/12/15/building-a-simple-asp-net-page-based-sharepoint-application-in-visual-studio-with-the-visual-studio-extensions-for-wss-ctp-1-1.aspx

http://blogs.msdn.com/erikaehrli/archive/2007/04/05/ASPNET2.0WebPartsAndWindowsSharepointServices3.0.aspx

ASP.NET on Sharepoint - WSS 3