Manage your App IDs in the Apple developer provisioning portal
App IDs are "the herpes of iPhone provisioning". Once you've created one, you're stuck with it for life. You can't edit it or delete it. By the time I realised this, I had way more than I needed.
App ID Sanity is the cure! It's a simple browser extension that adds the ability to rename an App ID and mark an App ID as inactive (which hides it from the App ID drop-down when creating a provisioning profile).