Wrapping an ice cube in a washcloth works pretty well.
You can also get one of those mesh teething bags such as this one.
http://www.amazon.com/Sassy-Teething...=baby-products
You fill it with ice or frozen fruit.
Babygirl™ loved to chew on frozen bananas.
The other trick is the old fashioned whiskey trick. Just dip you finger in some whiskey and rub it on the little tyke's gums. Call me crazy, but it did work in extreme circumstances.