Letterhead Examples:

Both of these sites show good examples. Some of the examples are too elaborate, however, because they
don't leave sensible room for people to type the actual letter. So remember that the main purpose of a letterhead
is to type the message/letter. It is not a flyer

https://www.pastemagazine.com/articles/2015/03/25-examples-of-excellent-letterhead-design.html

http://www.stocklayouts.com/Templates/Free-Templates/Free-Sample-Letterhead-Template-Design.aspx

 

Business Card examples:

http://www.howdesign.com/how-design-blog/best-business-cards