How can I customize the list of services that pops up when I choose to "share" something in an app?

Many apps give you the option to "**Share**" whatever it is you are looking at (or watching or listening to). This usually manifests in the form of a popup list of services that include: Gmail, Facebook, Twitter...) The list seems to be the same from app to app. How can I change what services are listed on this popup screen? Is there any way to change, add, remove, append this list? I'm running Android 2.2 on a Moto Droid 1.