http://www.smokstak.com    Forums, old engines, tractors, steam, etc.
http://www.greenmagazine.com    All things John Deere magazine
http://www.tractordata.com    Misc. tractor data
http://www.two-cylinder.com    John Deere two cylinder magazine
http://www1.caseih.com/northamerica/PartsService/Pages/search.aspx    Online Case International parts catalog
https://webparts.pvassociates.net/cnh/webparts/main.php    Online Ford parts catalog
http://www.agcopartsbooks.com/EpsilonWeb/login.aspx?ReturnUrl=%2fEpsilonWeb%2fhome.aspx    Online Agco, Allis, Massey, and other brands parts catalogs
http://www.electricalrebuilders.org/    Electrical rebuilders association website
http://www.oldengine.org/members/diesel/front.htm    TONS of interesting information
http://www.jdparts.com    Online John Deere parts catalog