As an exclamation, joder can be translated as 'fuck', but it is considerably less crude and often better translated as 'hell', 'heck', 'shoot', 'damn it', 'shit', etc. In colloquial register, especially in Andalucia, it is often contracted to joer, joé; it is also expressed euphemistically as jo, jopé, jolín or jolines.
-¡Joder! No tengo cobertura — Fuck! I don't have any coverage
-Es un problema, sí, pero joder, tampoco es para tanto — Yes, it is a problem, but heck, it's not that big a deal
-Pero ¿cómo quieres que no me preocupe, joder? — How do you expect me not to be worried, for Christ's sake?
-¡Esto hay que celebrarlo, joder! — Hell, this calls for a celebration!
-Carlos, te toca limpiar -¡Joer/Joé/Jo! — Carlos, it's your turn to clean -Crap!/Darn!/Oh!
-¡Cómo vuela este coche, jolín/jolines! — This car sure flies. Darn!/Jeez!/Wow!/Whoa!