Foto related
Glued lens – disassembling-assembling link
Norland optical adhesive NOA 61
classical repairs kyphoto
Infrared photo IR-PHOTO.NET
Flash tubes –
https://www.xenonflashtubes.com/
http://rutubes.com/
http://donklipstein.com/donflash.html
Other
PDF editing
A VERY good, and useful software, for less money than the Adobe Acrobat: www.pdfsam.org I am absolutelly satisfied with it!
Electronics
Resistor calculator – serial/parallel
Ismerkedés a PIC18 mikrovezérlőkkel
http://esca.atomki.hu/PICula/index.html
DIGITAL CANON repair blog 
i had little crack on home button flex cable it is iphone 6
is it possible fix flex cable with same chips and home button