Greg Schulz has an excellent piece on Top ten ways to secure your stored data.

There's a whole range of advice here, from ensuring that your physical security is in place and effective, to using encryption.

There are also some less well used solutions, such as ensuring that your backups and archiving solutions are also secure (and the method used to transfer and store tapes is also secure).

Best of all, he argues that ensuring that the mechanisms used are not a barrier to actually using and accessing the data.