Hi all,
 
I've decided to sell my Roland JD-800 keyboard and figure that eBay will be the best way to do it. Where do you get a box big enough to ship something like this, and do you have any advice on how to pack it?
 

A big box and lots of plastic peanuts. Or go to a shipping service (both FedEx and UPS offer the service) that will pack it for you.

Hi,
 
That thing looks interesting!
 
I think I am too much of a beginner to be able to use one of those!

Stop by a music store and ask about getting a shipping box or two.  When I was selling all my gear (and even when I was moving) I used a lot of those Kaman shipping boxes.  I usually just call up GC and ask for a manager.  They tend to tell me what days stock comes in and will either put a few aside for me (before they are broken down by the staff) or let me grab a few (I need to be there when they're unpacking).
 
One note about eBay, the shipping costs have gotten stupid and their calculators are very inaccurate.  I've stopped selling on eBay completely because of it (my last sale was a $30 item going from Vancouver WA to Michigan - it cost me $6 to sell that item because of how far off the shipping ended up being).

Thanks for all of the advice guys - much appreciated!

Moshkito
Hi,
That thing looks interesting!
I think I am too much of a beginner to be able to use one of those!

I've never done more than mess with presets myself. I bought it for the Strings expansion - just gorgeous. I'm basically using it is a MIDI controller, which is silly. I plan to sell it and get the Komplete Kontrol S61 - a much better studio tool for me.