Cafe World is pledging 50% of all proceeds from its "Save the Gulf!" Mystery Crates or 3 Special Charity items to the Audobon Society to fight the Gulf Oil Spill. Each Mystery Crate costs 16 Cafe Cash, or basically, a little over $1 USD. But Cafe World sells Cafe Cash in batches, such as 25 for $3.50 USD or 780 for $50 USD.
The 3 Special Charity items are pre-released items from prior theme sets -- Lobster Tank (25 Cafe Cash), Modern Fish Tank (22 Cafe Cash), and Primal Fish in Tank, which costs the same as a Mystery Crate.