Whenever I do a clean install of Mac OS, I pretty much only backup my Home directory. It contains all these things:
-pictures (iPhoto library in Home/Pictures/iPhoto Library)
-music (iTunes library in Home/Music/iTunes Library)
-documents (Documents directory)
-Address Book contacts (the Home/Library/Application Support/AddressBook directory)
-Mail email (the Home/Library/Mail directory)
-Safari bookmarks (the Home/Library/Safari directory)
If you don't have the original install CD's or files for your applications, backup the /Applications directory as well.
I'm not sure what you mean by "my share", though..