Unfortunately, AFAIK there is no way to remove non-App Store apps in Launchpad. Holding option on Launchpad gives you the wiggle mode and a little x on the app store icons to remove them.
I fully expect this to be fixed in 10.7.1. There is a way to do it, but it's a real pain in the ass. You can go in and edit the db file that Launchpad stores it's icons in, but they come back when you add a new app to the applications folder