TIP: How do I type the copyright symbol ©?

Mac

Simply enter Option + G.


M$ Windows

Whilst Num Lock is on, hold down the ALT key, keep depressed and type on the Numeric keypad '0169'.

Linux

This works on (k)ubuntu at least, using a UK keyboard.

AltGr + Shift + C keys.


Addendum

The above Linux solution did not work in GIMP for me when I was trying to create a Watermark for my photos.  The solution was to do the above in something like Kate (text editor), highlight and copy it to the Clip board and then paste it into GIMP's text editor window.