Just because everyone agreed during the meeting that certain actions would be taken doesn't mean they will actually do it. Priorities change, holidays approach, and other meetings might get in the way. A gentle follow up is sometimes a good reminder that something needs to be done. Look at the deadlines identified for each action item and check with each owner a few days before to see how things are going.
In some organizations where e-mails rule, a good way to follow up on action items and make sure they are being taken care of is to simply send an e-mail reminder. Something with the subject "FUP on Action Item…." stating in the body of the e-mail that you are simply following up and want a status update might suffice.
In other corporate environments, you may have to personally talk to the action-item's owner for a status update.
Instant messaging, now prevalent in most companies, can also come in handy when following up on action items. Open a new IM window and casually...