for married people - children
for singles - arts or entertainment circles
safe subjects with little chance of offending your group.

Religion and politics...... NO, just kidding, do avoid these at ALL costs!
Good subjects: Travelling i.e. experience of different countries - Childhood experience - "Anyone know a good joke?" often starts something... - Univers/ life elsewhere? - Energy - Global Warming.
Really depends on the company you're in so you should try chose the topic according the the people you want to converse with!