Here's a system I call "KeepYourSecrets.org". Recall a film noir detective telling the criminal mastermind that unless he drops a postcard in the mail in the next three days, all the details will go straight to the newspaper.
You can upload any kind of file -- it's all treated like binary. You can set some parameters like a distribution list and a checkin frequency. The system uses an IRC-like network to split your file in n parts, of which some k parts are needed to re-create the original. Up to n-k parts can be lost or compromised without losing or compromising the whole. (See "Applied Cryptography" for details.) With lots of hosts, you can split a document into multiple overlapping sets of pieces to provide another layer of resiliency against damage.
From then on, if you do not check in with the network on some periodic basis, the document goes out to the distribution list. NYTimes, Washington Post, CIA, whoever is on the distribution list for your file.
The network of server don't ever have to know who you are. They just need to know that you hold the private key that matches the public key that was used to upload the package.
It's possible to construct voting algorithms that the servers can use to decide if you have really checked in or not. This lets the network protect against a single compromised or hostile host. (You have to be resilient against hostile implementations.)
Because the hosts all communicate via some pub/sub or relay-chat protocol (Jabber, maybe?), the networks of hosts can be self-forming and self-identifying. If there is no central point of control, then the network as a whole cannot be stopped, subverted or forced to give up secrets by any single agency.
What you end up with is a secure, anonymous drop box that cannot be blocked, traced, or inflitrated. It is self-forming and highly resilient to the loss of constituent pieces.--------