a cheap inflatable pool raft (they fold up nicely and make the hard floor a lot more comfortable).  Keep in mind that in some airports sleeping on the floor is a no-no.

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an alarm clock or a pen and post-it pad.  If you are travelling solo, write a “Wake me at 5:00 AM” note and stick a few on and around you — it works.  People will wake you.

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an airline blanket and/or pillow (borrowed - NOT STOLEN!!!).

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Briliant (source, via Mel whoes blog is private)