Is there a way to send docs to your iPad (iBooks) via an email address endpoint like Amazon has for your Kindle?
Not directly to iBooks, no. But you can email it to whatever email account you have set up on the iPad. Then, using the Open With button you can send it to iBooks or any compatible app on your iPad.
I do this all the time with whitepapers I find on my work computer that I want to read on the train. Alternatively, I send my self a link to the file if it's not behind a paywall or lead generation form.