I know many people already know this shortcut but after reading a RIM Knowledgebase article about it I thought I would share it again.
Many companies such as Fed-Ex advertise their numbers like 1–800–GO-FEDEX. The problem is that BlackBerrys do not have the traditional 3 letters per key of other cellphones.
This problem is simply solved by holding the ALT key down while typing in the letters in the phone application.
Simple as that. You can even add phone numbers to your address book this way.
You can read more about it on the RIM Knowledgebase.