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hold down on one like you do to re-arrange the icons on the home screen and black circles with an "X" will pop up - hit that to delete it.
 
Open iTunes program
Delete it from Applications list
Sync and it will be uninstalled from your iPhone

Or in the iTunes program have your iPhone connected and select it (as if you were going to Synch it. Click the Applications tab and change from "All applications" to "Selected Applications". Check the apps you want on the iPhone and leave the ones you don't want unchecked. Now click Apply and your iPhone will synch removing the app from the iPhone, but leaving the app in iTunes (in case you want to add it back at a later time).
 
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