There are links to core exercises here: http://www.beginnertriathlete.com/cms/article-detail.asp?articleid=631. Click on "core 1" "core 2" or "core 3".

But...you can't spot reduce. Doing ab workouts won't lessen the amount of fat around your midsection, it'll only strengthen the underlying muscles. If you want to lose fat, you need to eat less and exercise more.