Recently, a whole collection of previous unseen and extremely rare Acid Test posters and handbills has been discovered, including a couple pieces of original artwork by Jerry Garcia. Included in this collection was an original hand-colored handbill for the Palo Alto Big Beat Acid Test, as well as a Poster for Mother McCree's at the Tangent in 1964, a Poster for the Warlocks first paid gig at Magoo's on May 5, 1965, a poster for the Warlocks fourth performance at Frenchy's on June 18, 1965, Phil Lesh's first gig. A set of tickets for the In Room in Belmont on Sept. 1, 1965 and a poster for the first Acid Test at the Spread in Santa Cruz on Nov. 27, 1965 as well as a Fillmore Acid Test handbill and a handbill for Carthay studios in Los Angeles on March 19, 1966. It also appears that Jerry Garcia designed several of these items himself.
The site that features all of this and more is here: http://www.postertrip.com/public/department37.cfm
There are 33 pages altogether, which can be accessed from the main page.

The whole collection can be viewed here : http://www.postertrip.com/public/5591.cfm

Further details like the Jerry Garcia original artwork can be viewed here:
http://www.postertrip.com/5584.cfm