Is there a keyboard shortcut (or way to set one) that allows to easily switch between different email signatures in mail.app ?
Sorry to dig up an old question, but I had the identical issue today and this was the first result for my google search for “mac mail signature shortcut”. While these answers weren’t what I was looking for, the 3rd google result was a MacWorld hint, which offered the perfect solution.
Here’s the answer: you can assign keyboard shortcuts for your email signatures, “From:” account selection, and even SMTP account from System Preferences → Keyboard → Keyboard Shortcuts → Application Shortcuts. To set up your shortcut, click the + icon, select “Mail.app” from the Application drop down, enter the text of the signature (or other option) as it appears in the New Message window drop down, and give it a keyboard shortcut. Rob Griffiths, the author of the MacWorld hint, advises using ⌃ (control) in combination with your desired keys to avoid conflicts with existing Mail shortcuts, which seems smart.
In my case, I created a shortcut in Mail.app for the menu title “None” (the first option under signatures) and assigned it the shortcut ⌃X. It is now exceedingly easy for me to clear my default email signature when it doesn’t seem appropriate.
For the purposes of illustration, here is the System Preferences → Keyboard Shortcuts pane (it’s the last item):
And here is what it looks like in Mail’s New Message window:
In "System Preferences", go to "Language & Text." Under the "Text" button, you have "Symbol & Text Substitution." You should be able to setup a substitution there.
Having said that, I use TextExpander, which is also a paid app ($35). I find it to be very worthwhile.
I use TypeIt4Me for all kind of text - also for my mail signatures. It is like in the AutoCorrect in Word where you type some characters, and they become replaced with the actual word/phrase - this one just work in all Applications.
Another one that do the same replace thing is Typinator - but I haven't tried that one my self.
They are both paid Apps.