Oh man...there's so many apps out there.
http://www.simplespark.com/catalog/?search=doc
http://www.simplespark.com/catalog/?search=calendar
http://www.simplespark.com/catalog/?search=note
My uneducated tip would be to not hold anything valuable online unless you want to become an early adopter. Web 2.0 apps die and born just as fast as flies and the coming recession is going to do more dying and more borning than ever.
If you must have a choice, IMO the current stable ones are: (Even Google was stable before they dropped support)
Docs: Zoho Docs, GreenDoc, Scribd
Notes: EverNote, Wetpaint, TiddlySpot, Netvibes
Calendar: None
Edit: Btw syncing tools are where it's at right now. If you must have online stuff, DropBox it IMO is much more stable right now.