To open a KML or KMZ file in Google Maps, I append the following prefix to an online link of the KML file: http://maps.google.com/maps?q=
Typically, I put the KML or KMZ in my dropbox, and then copy/paste the pulic link to the end of the above snippet. Then I can email that link to whom ever wants it, or I post it online somewhere. I've also used Google Docs to store the KML's, and a Links page on my website to distribute the links.
Example:
Harvey Mountain Hike: http://maps.google.com/maps?q=http://dl.dropbox.com/u/359140/KML/HarveyMountainHike.kmz