I hate rattles so I use a lot foam rubber drawer liner (looks like little waffles) to place under/around items.

For securing removable items:
Bungee cords
Velcro double sided 'tape'. I am using this more and more.
Polypro web straps. I HIGHLY recommend these straps: Rafting > Accessories > Straps at nrs.com
(I hate ratchet straps)

I use Velcro Extreme tape for small items on the dash,

And for securing more permanent times I quite often use nylon ties, especially 175 lb ties.

Toy Man