How to easily type the circled B symbol on a Mac
There are several ways you can enter the ⓑ or Ⓑ symbol on a Mac, depending on how frequently you think you will do it.
If you think you might type it a lot, the quickest way is to open up a Terminal window and enter the following two commands:
mkdir ~/Library/KeyBindings echo '{ "~b" = ("insertText:", "U24D1"); "~B" = ("insertText:", "U24B7"); }' >>~/Library/KeyBindings/DefaultKeyBinding.dict
You can just copy/paste them if you aren’t sure what they mean.
This sets up MacOS X to recognize Option + b as the lowercase encircled b character ⓑ and Option + B as the uppercase equivalent Ⓑ. After running these commands you have to restart applications for them to pick up the new keybinding. It only works for Cocoa applications (which is nearly all of them these days).