Haven't found the exact fit yet, but here are a few sites I think might be useful to others who like to organize:
Backpack offers free accounts, and allows you to store to-do lists, notes, ideas, and your calendar online. This one looks like something you could use as an idea mapper and collaboration tool, too (recommended by Debbie Ridpath Ohi.)
Inbox.com is a web-based e-mail service that gives you a free 5GB account for registering; their free online organizer looks pretty nifty, and might work as a virtual whiteboard.
TiddlyWiki is a free service that provides a reusable non-linear personal web notebook (LJ Cohen did a terrific virtual workshop back in July on how to use TiddlyWiki to organize your novel.)
Does anyone out there use an online organizer service that is free or low cost and that you'd recommend? Leave a link in comments if you would, please.