For the "3 days a year" Jews, Rosh Hashanah and Yom Kippur are over so that's the end of their shul attendance until next year. But the original reason for those holidays was to prepare for Sukkot, the big harvest festival, which was culminated by Shmini Atzeret.
So for some of us, that means that we are back at shul yet again. But it seems that many readers and posters of this forum are not members of a congregation and/or live far from any Jewish centers or synagogues. So especially for people who will not be able to celebrate the holiday communally, "Judaism Unbound" could be a helpful online resource. It has readings, podcasts, and videos on many Jewish topics. Here is the link to the page with resources for "High Holidays": Judaism Unbound: High Holidays All of the resources are for Rosh Hashanah and Yom Kippur, and nothing on Sukkot let alone Shmini Atzeret, so this post is a little late, but I had forgotten about this website which I found out about right before Shavuot until I was going through my list of web links that I wanted to save for later. And I figure that the people without a Jewish community may have missed a more involved observance of those other holidays previously, so these resources might still be of interest.