We have a much better idea of what digital technologies and formats will last into the future than we did in the 1980s. Pick reasonably open formats and standards that have been around for a long time, and are used every day. HTML has been heavily used for more than 20 years, and it's only getting more widely used. UDF (the DVD file system) has been around for almost 20 years, and ISO 9660 (CD file system) even longer. Better yet: mix, match, and do all of them!