I found this app very useful, uploading it soon after feeling the earthquake here in Southern California on April 4. You can use a list of the latest earthquakes to get information (not detailed, but good enough), or tap on the map. Both are useful.
The database from which they pull the data is very good (I believe the USGS), and it's kind of cool to look at earthquakes across the world. Of course, most earthquakes are not related to each other, but you can see local swarms. For example, the April 4 earthquake in Baja California is still sending out several aftershocks per hour, so you get a huge splotch on the map.
This is the "lite" version, so I'm assuming that the full version will be more fun. I'd like to see earthquake depths and longer history (I'm not sure how far back the data base goes) which is easily accessible.
Anyways, for those of us on the West Coast, it's a very useful tool. Once the iPad store is open worldwide, I'm sure people in other areas of the world will buy it. We used to have office pools on the Magnitudes of earthquakes...this will make paying off much better (yes, after a few hundred earthquakes in my life, including quite destructive ones, but most Californians have a callous attitude towards them).