Mutual funds.. Why does their share price only change once per day?
 

After following a few mutual funds on a daily basis, it seems that they generally start the day with a "open price" (obviously), and close the day at a different amount. However, throughout the day, the price doesn't seem to fluctuate at all..

Is that generally how mutual funds work? IE, the closing price will be a representation of what all the individual stocks within the fund did in a day, and as a result, there will only be a single change in the share value, as indicated by the closing price?

Yes. Also, most mutual funds (not all) can only be bought or sold at the day's closing price. Thus, there's no need for continuous calculations.