To any Jewish readers, have a happy Shavuos.
To the non-Jerwish readers, Shavuos is celebrated for two days in the diaspora and it's a mitzvah to attend services to hear the Ten Commandments read during the Torah service.
It's a Jewish custom to only eat dairy during the holiday.
It's a mitzvah to stay up all night on the first night to study Torah. As such, here is a link to all 613 positive and negative mitzvot.
Here are the ABC's of Shavuot.
Did G-d speak at Sinai?
Here's an entertaining video.