I want to put items in the site tree that don't actually link to any pages.
When I'm just continually adding pages , it looks unorganized to have like 20 items just hanging there that are uncategorized.
I want to put like..
Login / Registration
Otherwise it'd just be pages uncategorized and hard to read.
Well there isn't much you can really do except not put them in the sitetree but make the include files in your template directory, but then obviously you can't edit them online.
If you want the ability to edit them online, then they'll have to show up in the sitetree so you can access them. Best thing to do would be just to put them all as a sub page of one parent and remove the option for 'show in menu' so they don't show up in your navigation.