hi i got bit of an idea about this.........topic
we need to add intent filters for this purpose............
suppose we want to associate an application with .doc files then we can simply do that by adding this to Androidmanifest.xml file
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.BROWSABLE" />
<data android:host="*" android:mimeType="mytype of file,will get it from file properties"
android:scheme="http"android:pathPattern=".*\.doc" />
</intent-filter>
if u have any doubts check manifest file of fbreader
[font=Arial Black] [/font]
http://www.fbreader.org/FBReaderJ/