Just noticed this thread after someone linked to it. For the last year and a half, I've been writing and recording a 100-word story every week, in response to a prompt word, and sending it off to a web site that runs a weekly drabble challenge. I use a proper voice recorder for this (the Edirol R-09), and do as many takes as it takes to get the best possible result.

I don't just record them once a week, with 80 stories in my head by now I often just recite them for practice when I'm alone. Less work than picking up a book to read aloud from. If you don't write, memorising poetry would provide the same advantage.

I used to find that my voice was fine first thing in the morning, but tended to get very hoarse by mid-morning, but that has abated substantially. Maybe I just don't talk enough otherwise to keep it exercised. I don't actually do enough talking in everyday life that anyone has spontaneously commented, but I have had a few compliments in the comments at the web site.