Distributing Customized Items (XSISDK)
If your customization is very simple - just a single self-installed plug-in, toolbar or other file, then you can send it around by email or place it on a Workgroup. XSI auto-detects/auto-installs customization files when it restarts.
For complex customizations involving multiple files you should organize the files into an Addon directory. Then you can package the Addon directory into an .xsiaddon file or you can move the Addon directory onto a shared Workgroup location.
If you wish, you can also create your own custom installer program with Perl, for example, and Install Shield etc. As long as it places the files in the correct location (e.g. in a subdirectory under the Addons directory of the user or workgroup location) then XSI will find the files when it next starts up. See the SDK reference for infromation about finding the installation location of XSI from the Windows Registry.