Here are some of my favorite links for working on my Datsun 240z. These websites and forums all have a wealth of knowledge to draw from.

Forums

Hybrid Z

Classic Z Car

Websites

Datsun Z Garage (engine building and modification tips)

Part SupplieRs

Classic Datsun (Datsun racing and period correct parts)

Z Car Source (Datsun part suppliers)

Z Specialties (Datsun part suppliers)

Motorsport Auto (The Z Store - Z Car specialty store)

Arizona Z Car (Datsun Z upgrade parts)

Zeddsaver (Datsun Z part suppliers)

JDM Car Parts (Datsun part suppliers)

Techno Toy Tuning (Suspension upgrade parts)

Z Car Custom's JDM (Datsun part suppliers including JDM parts)

Robello (Engine Builder)

Datsun Spirit (Engine Builder)