I've just created a tag wiki for speech-recognition (should be under review by now).
I propose that we merge speech-to-text and speech-recognition into speech-recognition because it is the most commonly used term for this kind of technology. (I deal a lot with speech recognition professionally and all the English language forums nowadays call it speech recognition.) FWIW, the Wikipedia entry also lists speech recognition.
Possibly, to prevent future complications, let us also use voice-recognition - currently non-existant - as a tag synonym for speech-recognition.
EDIT:
I leave the previously proposed merge of voice-commands open for discussion, because while voice commands are part of speech recognition, they can also exist in software not intended for text creation - such as Dragon oder Windows Speech Recognition, but in "pure" command tools like Speakable Items on Mac. However, some people might associate voice-commands with speech recognition for text creation - because you command the computer to write.
My argument in favor or merging voice-commands with speech-recognition is that both categories exist in small numbers, so an overly fine distinction is not warranted. However, the "small-number argument" might not be considered relevant by others.
text-to-speech (TTS) should not be merged because it describes a different technology. speech should not be merged either, because it most often used in the contect of TTS on this site.