For good background information, the Storage Network Industry Association is a great resource with a number of different publications, books, and presentations. (I could also suggest portals such as SearchStorage.com are good, too... but that would be a little self-serving.)
Other good sources include storage consultants (generally paid engagements), companies like GlassHouse Technologies and others that have developed best practices that are vendor-agnostic.
The third choice is the vendors themselves... You just need to understand the source when recommendations are made that promote a single vendor approach.
This was first published in January 2003