If you own a 1970 Sportster, you should belong to:
http://www.onelist.com/group/1970-Harleys One List is a very small group of 1970 Sportster owners. When you send e-mail to this list, everyone on the list will get a copy.
http://clubs.yahoo.com/clubs/theironheadsportstergarage The Yahoo Ironhead Sportster Garage is a group for Ironhead (1957 to 1985) Sportsters Owners. A great little club.
http://zoostation.cns.ohiou.edu/~dmans/moto/home.html This is a huge e-mail group. Lots of good information, especially in the archives. But watch your mail box. It fills very quickly.