If you do not have a website at which to serve your XML Schema file, you can always use a cloud service such as Dropbox or Google Drive, both of which will allow you to make a file publicly available via a URL.
- See How do I link to a file or folder? for Dropbox.
- See How to share for Google Drive.
If for some reason you do wish to package the XSDs with the program or XML files of your project, you can avoid problems locating the XSDs on different machines via
- Relative paths
- OASIS XML Catalogs