I actually find the full version of Microsoft Outlook very useful. I think it has functionality that most people don't take full advantage of, but that is true of many apps.
If you don't want the email part of it, I suppose you could probably set it up without the email account. I never tried to do that though, so you might have a problem with it asking you to do the set up.
Outlook has calendars with event reminders. It has portions for tasks, notes, contacts, folders, etc... You can even use it for document storage if you want. It is also searchable, so if you have a lot of stuff stored, you can find things pretty easily. Of course, to me the email just makes it that much more functional, so I would never set it up without, but to each his own.
"Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments" - Dunning and Kruger's Nobel Prize winning report