Luggage rack attachments for laptops? So, while out riding my bike, I really dislike having a backpack on.  I have a trek luggage rack on my bicycle and would love to find something that could attach to it, capable of holding a 17" laptop, preferably in a hard case, with padding.  I would really hate to lose the laptop (or its drive stability) to a fall/crash or even just the basic road vibrations and bumps...

Has anyone seen a product like this, or potentially know a good way to build something like this? :)
Your best bet for weatherproof and crash worthiness is going to be a pelican case. They have a whole series of cases for laptops.
http://www.pelican.ca/case_group_search.php?CaseGroup=Laptop

I've personally taken a 'hardback' case on a paddling trip and it held up great. Many pelican products also have a warranty against failure as well so if the product does leak you've at least got a new case and a replacement laptop.

If you get one of their other cases you can also lock the case which will assist in keeping it secure from a thief. Yeah it's not going to stop a determined person but at the least it will give you time to realize and change any vital personal information.

Past that make sure you backup your data with something like Mozy.com. At some point you'll have a drive failure no matter what.