yes...you just cant put 2 contextual ads boxes together, google doesnt want to compete with its rivals on the same page.
Just a little change on your post: You can put 2 contextual ads boxes together, but both of them would have to be from Google. You said that, but I wasn't sure if everybody would understand it the way you said it.
this one does too... (actually it's amazon and adsense) http://www.antwone.com (NOT MINE) Just an example...
I asked Google (via e-mail) about having Amazon ads on the same page with AdSense and they said no problem. I didn't ask about eBay, but if it works the same as Amazon, it should be just fine.