I started working on software to do this a few years back. I concluded that all the software is already written if you have a need and the problems are all regarding the way the user wants to protect the information, how much money they have to spend and how careful they are. In other words, it's a social/societal problem and you could setup a consulting service to help people do it, but software probably wouldn't be much benefit.
Here is an example:
First encrypt all the things. Then give the encrypted file to anyone since you're going to assume for the sake of this slashdot post that the crypto is unbreakable (if you're unwilling to accept this assumption then feel free to divide the data the same way the key is outlaid).
Next establish some trusts in your name and appoint a number of people as trust managers. This should probably be more than one trust and definitely more than one person. You may even need to obscure who creates the trust depending on what you're hiding and who might want to get it. Try to make some of the trust managers overseas might be good if you're worried about long term survivability of your data, since stability of a country might be in question in 100 years or so.
Now, cut your key into two halfs (or more), write out instructions that the managers are to meet at some location at a certain date. None of the managers should know any of the other managers. For survivability you might give a duplicate copy of parts of the key to multiple people so if one person doesn't show up there is still a chance to recover from it.
Ultimately nobody has knowledge of anything. On the date in question the responsible people show up only with the knowledge they are supposed to arrive with their bit of information. It could be that they don't arrive anywhere at all and their instructions are to publish the information. Without having context only the receiver would know what the completed key was for, and even they might have only been instructed to hold on to data for 100 years then accept the key when it arrives.
This scheme works best if there are multiple companies around the world formed with the purpose of doing this for people, or if it was a common service asked for at banks/law offices/etc. If the lawyer is holding on to only one key for 100 years they might become curious and try to figure out what it's for. If it's one key amongst thousands then it's nothing more than a tiny amount of data they're paid to deal with. They would also be less likely to publish the information out of turn because it could be they're storing it for something worth less than the amount they're paid to escrow it.