I want to built an application for crossword puzzles and want to know
if there are any sources of crossword puzzle content (questions, ie)
that I can use/syndicate as I don't want to create all of them myself.
 Want to know if there are any sources of sydnicated data for
crossword puzzles (xml, text or other).

I'm doing my dissertation on 'Representing Crosswords using XML
technology'.  I searched & searched for XML crossword data like you,
then I came across:

http://webcrosswords.com/

The home page consists of a flash document, when you view the source
code and search for 'swf', it says:
xword_online_mx1.swf?dt=060424&xurl=xw_control.xml

Whats todays date: 24th Apr 2006, that shortened & backwards is
060424.  Next was the hard part, I knew that uclick generated a lot of
puzzles on the internet & webcrosswords.com was 1 of them.  Eventually
I came across this:

://www.google.co.uk/search?q=uclick+%2B+%22-data.xml%22&start=0&ie=utf-8&oe=utf-8

Uclick have loads a xml documents in the 3rd link down, I looked about
on the directory until i came across 'fcx' directory, then under
'data', hey presto:

http://www.uclick.com/puzzles/fcx/data/?C=M;O=D
(this lists the last modified 1st)

These xml (-data) documents generate the webcrosswords.com page, eg:

http://www.uclick.com/puzzles/fcx/data/fcx060424-data.xml
powers:
http://webcrosswords.com/xword_online_mx1.swf?dt=060424&xurl=xw_control.xml

Let me know how you get on mate, I created crosswords using these XML
files, using XSQL & XSLT.

HOPE THIS HELPS