Article on VSTO
http://www.awprofessional.com/articles/article.asp?p=417510&seqNum=4&rl=1
VSTO Sample Chapter
http://www.awprofessional.com/content/images/0321334884/samplechapter/VSTO.pdf
Create Estimation Solution using VSTO 2005
FAQ
http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=223585&SiteID=1