Interesting calculation I made: The general custom is to sound the shofar one hundred times on each day of Rosh Hashana, except for Shabbat. (OK, our shul blows it a few more times, but let's talk generally.) In addition, we blow it on two other occasions, in both cases four times: Every weekday morning of Elul, starting yesterday, and at the end of Yom Kippur.
Now, Elul has 29 days. We don't blow the shofar on the last day, leaving 28. In any 28-day period, there will be four Shabbatot, so we blow it on 24 days in Elul. (The last day of Elul can never be Shabbat, so all four Shabbatot will be in the 28-day blowing period.) Add Yom Kippur for the 25th day, multiply by four, and you get...another hundred, exactly. Interesting.
Stay tuned for...oh, I don't know: My calculation of how many times, exactly, we hit our chests on Yom Kippur. :-)