“Your tablet is waiting.”

That was the subject line of the e-mail that landed in my inbox at 4:36 a.m. Monday.

It came as a surprise to me, because the last time I checked, the iPad 2 that I finally broke down and ordered on March 23 wasn’t scheduled to ship until April 21.

So I took the bait, opened the e-mail, and got roundly switched.

Staples (SPLS), which bills itself as “the one place that makes technology easy,” is not on Apple’s (AAPL) list of approved iPad resellers. And since the iPad 2 assembly lines can’t keep up with the crushing demand, Staples is trying to slip through the window of opportunity with its “your tablet is waiting” campaign.

But Staples’ tablets have supply problems of their own. Only one of the three items it describes as having “arrived” — Motorola’s (MOT) Xoom — seems to be in stock. The other two — from Research in Motion (RIMM) and Dell (DELL) are available for pre-order only. And one of them, the BlackBerry Playbook, hasn’t even been released.

Also on Fortune.com:

• iPad 2: Out of stock by Saturday
• Thousands in London queue for iPad 2
• Videos: iPad 2 lines in Europe, Canada

[Follow Philip Elmer-DeWitt on Twitter @philiped]