If you add this line to your .htaccess file:
AddType application/x-httpd-php .html
.html pages will be able to execute .php commands. :)

This works & it might be the only way: http://www.boutell.com/newfaq/creating/forcedownload.html

It is quite a bit easier to link to a .zip file that the browser does not know how to open, thus...

There are a few web pages setup to do this for us... here is one of them:
http://corz.org/machine/source/php/tag-tools.php

Rotate Image - I assume you mean randomly display an image from a list of images as opposed to actually rotating the image 90 degrees or something, right? (If not we can help with that too).

In...

There are many place for free hosting, but most of them are not very good. This may be an ok solution?

If not, perhaps you have broadband and leave your Mac turned on 24/7? If so, you might...