Are there any commonly recognized "great" CEO letters in annual
reports?  I know that Warren Buffet's letters are highly lauded. 
Please let me know if you know of any other great ones.

One way to find this also might be to contact companies
that prepare annual reports and see what they think.
In addition to analysts, their opinion is probably very
valuable since they have seen such diversity of
entrants.  Good luck.

CEO letters at Amazon.com are highly regarded:

http://www.fool.com/News/Foth/2002/foth021119.htm

I work in an investment banking and the only letters that have ever
generated noteriety that I am aware of are Buffett's.  The only thing
that comes close are Ace Greenberg's company memos (memorialized in a
book).

That being said...google has an answer for everything -- sort of.

Apparently there is a guy who writes a newsletter regarding annual
reports!  Believe it!

http://www.sidcato.com/news/2003/rel0103.html
Apparently, he's an annual report/CEO letter guru!  I bet he has an
opinion about good letters!  Look him up and give him a call...

Here is a link to an article discussing the changing trends in annual
report letters:
http://twincities.bizjournals.com/twincities/stories/2002/10/07/focus1.html
The gist is basically to get down to business and lose the
"marketing-speak".

Lastly, here's a ranking of the best/worst annual reports from Chief
Executive magazine...
http://www.chiefexecutive.net/bench/bwannual/161_10_best.htm
Figures, its written by that Sid Cato guy.  Sounds like he's your
man...