I plan on going to Oshkosh again this year. I enjoy getting there a
couple of days early and sit near the flight line and watch all the
planes arrive. I think it would be more enjoyable if I had a scanner
to listen to air traffic control. Could someone recommend an
inexpensive scanner for this purpose. Where would be the best place
to purchase said scanner?

I have a Radio Shack scanner (not a cheapie) which was about $200.

The year we went to Oshkosh, one of the tent vendors was offering several such
scanners, seems like the cheapest was about $35, which may have been more than
it was worth (I believe it hissed all the time - no squelch)...plus at least
one additional more expensive scanner.

Watch the Radio Shack ads.

I've lost track, but do Uniden and others offer scanners available through
WalMart and places like that?

"A profound statement of the obvious...": make sure it picks up the aviation
band - not all do.

Also watch the 'nickel shopper' classified ad papers- every now and then
someone has one they just want to convert into cash, to buy groceries, no
doubt. And it probably isn't stolen...

If I were you, I'd just buy a new one at Radio Shack...after all, you can
afford to go to Oshkosh...