IC (integrated Circuit)

Timer  IC,  Op-Amp

NE555    Timer  
UA741    Single Op Amp   
LM348    4  x  UA741 Op Amps  
LM324    4 x Op Amp (single supply)  TTL compatible  

 Common TTL Logic IC 

74LS47     Dual Positive-Edge-Triggered D Flip-Flops with Preset/ Clear and Complementary Outputs 

Opto Couplers 

PC817         LED / Transistor 
4N25           LED / Transistor 
4N33           LED / Transistor
MOC3021    LED / DIAC