Tisha B'Av begins at sundown on Saturday, July 21st
There are some beautiful writings on the internet about this holiday. To learn the basics you can visit Chabad, Wikipedia, or even My Jewish Learning.
But my favorite comes from Ritual Well, a piece called The Lament of the Twelve Sisters.
And I'll end with this excerpt from a poem by Rabbi Patt Haskell
"...Ancestors' sobs echo through winding old city streets
Then settle here, to mingle in my modern ears,
Over thousands of years, over thousands of miles.
The breaking of ancient hearts reflected by cracks in mine.
I am the diaspora.
I am your pain.
Though I've walked in your footsteps
I cannot remain...."
Read the rest here