How much yeast did you pitch? Was it liquid or dry? What were the OG's? Were they extract or all grain recipes? What was the exp date on the yeast? Did you make a starter, and if so how big? Did you aerate and how? What was your pitching temperature? These are some of the basics that can effect the speed/activity of the ferment?
I second what the above two posters said. For example I brewed an IPA on Saturday that I pitched 3 cups of thick slurry into straight from another fermenter. It was blowing out of the bucket at 5 hours. Now, about 60 hours later, the krausen is totally fallen and the bubbling is very slow. I'm about 0.002 short of where I figured it'd end at, but I'm going to leave it alone for a few more weeks before kegging it to condition.
While this isn't exactly "normal," nothing really is in homebrewing. I would say that you should probably let them be for another few days to a week, then take a gravity reading. There's a lot more than just fermentation that affects airlock activity. The temperature swings, the solubility of CO2 in the beer, atmospheric pressure, the list goes on...
Before you take any drastic measures wait a bit, then take the gravity. If it's not done wait about 3 more days and take another gravity reading. If both are the same and both are a lot higher than what was expected then it's time to get worried. Other than that sit back and enjoy the anticipation of drinking some good beer.