First off, what is an ECID and SHSH and why do you care? via iphoneincanda.com "Well “ECID” stands for Exclusive Chip ID. This is a unique chip identification that is different for every iPhone 3GS and iPod Touch 3g. When you restore your device, iTunes contacts the Apple servers, to generate signatures (SHSH), just for your device. It is widely thought that this a new security feature, implemented to stop jailbreaking of future firmwares."
With that being said, heads up, the next ipad firmware version will be coming out soon. Even if you do NOT plan to jailbreak (you really should), you should at least back up your SHSH files in the event you ever decide to sell it, or change your mind about jailbreaking. Since this is the first-ever firmware version for the ipad, this is a desirable SHSH to have, as it means no matter what happens to your ipad, you'll always be able to downgrade to 3.2 again, which means that you'll be able to use any and all jailbreaks that come out in the future. As the device matures, more people will be locking themselves out of the option of jail breaking, by not saving their SHSH files. And that means you can sell yours for more.
Here's how to do:
Put your pad into recovery mode and get the ecid, details here:
Run fwumbrella and enter your ecid. fwumbrella will download your SHSH keys from Apple.
Your SHSH key is the secure signature apple signs their firmwares with; if a firmware isn't signed, your apple device will no longer load it. And they stop signing them as soon as a new firmware comes out, so downgrading is no longer possible.
Update May 3rd, 2010 - Spirit jailbreak is now live, and Apple will probably stop signing 3.2 and 3.1.3 firmware VERY soon. To give one an idea of how soon Apple will respond: The SMS userland exploit was patched the very next day.