The Outside Lands festival has become an annual (2008-Present) August event. It is a three day music festival held in Golden Gate Park.

Here are some acts that I saw or wish I had been there to see. (full list available on Wikipedia)

Radiohead (2008)
Cake (2008)
Tom Petty (2008)
Pearl Jam (2009) — saw it
Q Tip (2009) — saw him
Tom Jones (2009) — saw him
Tenacious D (2009)
Thievery Corporation (2009)
The Strokes (2010)
Al Green (2010)