Winter: Sled dog racing
Summer: Sumo wrestling
I believe the ballroom dancers are trying to be an Olympic sport - seems reasonable to me.
Rugby 7s and cricket.
Summer: Ultimate frisbee
Bocce
Lawn Darts
Chess
Scrabble
“Guess My Weight”
Poker
Ninja Decathalon
In the paper I saw a recommendation for synchronized underwater ice fishing. I can’t improve on that. 
Why stop with ballroom?
Would it be possible to hold a reasonable tournament involving all the cricket-playing nations in just two weeks?
The World Cup seems to handle it with football/soccer. Plus, the Summer Olympics are three weeks long. There would be qualifiers earlier.
Golf.
I can’t understand why it isn’t an olympic event. It can easily be staged, it doesn’t require any infrastructure (Any city big enough to hold an Olympics has a world class golf course nearby), and it is a truly international sport. If it were held this year, any of these countries could theoretically win -
Australia
New Zealand
South Africa
Zimbabwe
U.S.
Canada
Argentina
Fiji
India
Japan
S. Korea
England
Ireland
Scotland
France
Italy
Germany
Denmark
Sweden
plus a bunch more.
…just thinking about it, a twenty/20 tournament would be quite exciting, although the purists, (like me!) might get upset, and at times the game really becomes one of good luck than of skill.
http://www.bbc.co.uk/insideout/eastmidlands/series3/cricket_countycricket_sport.shtml
…and ditto on Rugby Sevens…
Baseball!
IIRC, it was an Olympic sport at the start of the 20th century.
It was tried. Some of the problems with baseball in the Olympics were:
[ul]
[li]Major League Baseball wasn’t willing to interrupt their season to let players compete in the Olympics[/li][li]they couldn’t schedule enough games to have a meaningful tournament in the time allowed (remember that baseball teams use a pitching rotation)[/li][li]there are several countries in the world where baseball is a big-time sport, and the rest of the world doesn’t care about it at all[/li][/ul]
Major League Baseball is holding the World Baseball Classic - a sixteen-nation tournament that will happen in the middle of spring training. We’ll see how it goes. Some aspects of it are a little phony - for example, the Italian team has players like Mike Piazza who is Italian by ancestry only (he’s never set foot in Italy).
Eh, you can say the same thing for hockey.
Hockey’s very popular… or do you mean ice hockey? 
How about squash?
A traditional cricket match lasts five days, and an abbreviated one lasts eight hours. It would be tough.
I’d like to see powerlifting as an olympic sport, in addition to olympic lifting. The two are different enough that anyone who excels in both is a genuine world-class athlete.
The Cricket World Cup only consists of one-day matches. I don’t see why the Olympics couldn’t be the same.