What is a white elephant sale?

A white elephant sale is a bit like a rummage sale or a garage sale.
Typically such a sale is organized by a social group or a church for
fund-raising purposes. Members of the group bring one or more items
from their homes. The items are often weird or ugly things, the kinds
of things that other people might want, but that the contributor would
like to get rid of. The items are put on display and either priced for
public sale or auctioned to raise money for the group.

A variant on this is the white elephant party or white elephant gift
exchange, in which each participant brings something unwanted or
bizarre (the uglier the better) to trade with others.

"A white elephant sale in the States is normally a sort of odds and
ends sale where people bring those objects they have which don't quite
fit anymore (if they ever did). So you end up with a lot of stuff that
is of questionable design appearance and quality. There are those who
always find that someone else's 'white elephant' is their treasure."

Phrases: White elephant sale
http://www.phrases.org.uk/bulletin_board/33/messages/908.html

You may wonder what any of this has to do with white elephants. The
term "white elephant" for an unwanted possession is thought to come
from an Asian legend in which the gift of a white elephant brings
financial hardship to the recipient.

"From the A.Word.A.Day mailing list: 

1, A possession unwanted by the owner but difficult to dispose of. 
2. A possession entailing great expense out of proportion to its
usefulness or value to the owner...

From the perhaps apocryphal tale that the King of Siam would award a
disagreeable courtier with a white elephant, the upkeep of which would
ruin the courtier."

Everything2: White Elephant
http://www.everything2.com/index.pl?node_id=127675

"White Elephant 
  
Meaning: Something that is costly to obtain or maintain and provides
little benefit or value...
 
Origin: From the Burmese belief that albino elephants are sacred. They
can't be used for work and they must be lavished with the ultimate
amount of care. Giving a gift of a white elephant would be done to
someone considered an enemy.  The idea being that you would eventually
wipe out your enemy's wealth with the care of the sacred elephant."

Origin of Phrases: Special Interest
http://members.aol.com/MorelandC/HaveOriginsData.htm 

My Google search strategy:

Google Web Search: "white elephant" origin
://www.google.com/search?hl=en&q=%22white+elephant%22+origin

I hope this helps! If anything is unclear or incomplete, please
request clarification; I'll be glad to offer further assistance before
you rate my answer.

Best regards,
pinkfreud

Thanks!