This is more of a bookmark for myself than anything else but I thought I'd share -

.NET Framework 1.x

MS .NET SDK documentation -
http://msdn2.microsoft.com/en-us/library/system.web.mail(VS.80).aspx

The eternally famous -
http://www.systemwebmail.com/

.NET Framework 2.0

MS .NET SDK documentation -
http://msdn2.microsoft.com/en-us/library/system.net.mail(VS.80).aspx

And of course the sister site to http://www.systemwebmail.com/
http://www.systemnetmail.com/


CDOSYS

MS CDOSYS SDK documentation -
http://msdn.microsoft.com/library/en-us/e2k3/e2k3/_cdo_messaging.asp

CDOSYS and sending mail using port 25 -
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/e2k3/e2k3/_clb_sending_smtp_mail_by_port_25_using_cdosys_vbs.asp

The guys at PowerASP have heaps of handy examples -
http://www.powerasp.com/content/new/sending_email_cdosys.asp

CDONTS

MS SDK documentation -
http://msdn.microsoft.com/library/en-us/cdo/html/264c6b14-d93a-426a-be96-3a31c958e6c8.asp

More stuff at PowerASP -
http://www.powerasp.com/content/hintstips/asp-email.asp