I just found out there is a pretty awesome online todo planner system called Zoho Planner. This is similar to Backpack from 37Signals which you can separate different type of information and todo into different pages, you can then share it to other users. What it is superior is the ability to export it to iCal and also the unlimited space to attach files to your planner:
Zoho Planner is an online organizer to Plan & Organize yourself. Create your own space on the web, Organize yourself by creating new tasks & marking completed, Quickly post your thoughts as blogs, Interact with people, Create classified ads.
Zoho Planner has its potential to become a great planner because it can export to iCal which you can then import into your Palm and other PIM. Also the usability are pretty high as well. Hat tips to their engineering effort!