All the methods mentioned by TUAW involve acquiring at least a GB or disk space from (albeit one of them free) an online supplier.
They didn't mention another (free) system which I use to share my calendar with my wife and her calendar with me. This is iCal Exchange. iCal Exchange is designed specifically for sharing calendars from iCal - I've used it now for 2 months and have found it very reliable and easy to use. You can even log in to your account on icalx and view your calendars using a web based calendar system, you cannot edit though as iCal doesn't support this.
iCal supports both public and private calendards - private calendars require a username and password to be supplied and I think you need to pay iCal Exchange some money for this service, but the public calendars are free.
Give it a try - it makes some sense if you don't want to use an online disk service like box.net, jungle or .Mac - or hack your iCal with Scalp.
link to TUAW article
link to iCal Exchange