Tuffy's storage boxes are 'top notch'. Really expensive, but probably the best out there.
Another company is
www.jeepbox.com I haven't had a chance to browse their site much, but I hear they make pretty good stuff.
I had some ideas regarding making my own storage, security deal... In retail stores and showrooms, they have those colored 1" x 1" square display racks... the ones peg hooks kinda hang onto. Well I wanted to cut one to size of the trunk part. Bolt U-shaped supports at the back of it (behind the seats) and a latching mechanism at the tailgate side. This will offer kinda a shelf at the wheel well height and security underneath it. You'll be able to see whats there, but unless it's smaller than 1", you can't get at it. Certainly would be cheap. Steel grids are a good start on security, and it'll have area's all through out to strap down a million things on top of it (tent, sleeping bag, any other form of a bag, etc.)
If, and when I invent this, I'll show pictures of it.