To be joyful and celebrate is a mitzvah from the Torah, can you believe that?!
We are told to have a feast...and not just once a year!
There are 7 (or 8 depending on how you count) Biblical Feasts, of which 3 are Pilgrimage Feasts (marked with *) prescribed in Vayikra/ Leviticus 23.
Shabbat - Weekly!!
Unleavened Bread (7 days)
Sukkot* (7 days)
And there are additional festivals such as Purim and Chanukah that is not commanded in the Torah, but have great significance in history.
Understanding the calendar is of paramount importance if you want to keep the feasts at the correct times.
And remember that the day starts at sundown and ends at the next sundown.
You will find more info at all three these buttons.
The Annual Feasts
The wonderful thing in Judaism is that everything works in circles...complete the Biblical Year 14 days before Pesach in the month of Nisan, complete the secular year the day before Rosh Hashanah and complete the Torah cycle during Sukkoth. Truly a circle of life!
AishTorah's site is easy to use with loads of information. You will also find fun video's and songs for the holidays.
More Feast Info
Chabad has another point of view and loads to read on how and why we keep the feasts.
You can also find reading material for the weekly parsha in various degrees of depth:
From light overviews (the parsha in a Nutshell) to wisdom / kabbalah teachings.