You will never get a dot com for free, just not going to happen. Web site/space free, sure. But depends on which way you go.
If you want a full site, shopping cart, etc all done up free, keep dreaming. If you want to make your own site, free, and do it simple, then that is possible.
Cheapest way to set this all up to look professional, to get hits, to be found on search engines and other locations. Do the following.
Go to GoDaddy.com and buy your dot com of choice, $10 per year. You won't find it cheaper elsewhere. With this you will get a free matching dot com email and free forwarding.
Then go to www.WordPress.com and set up a blog. Make the name of the blog the same as the dot com as this helps w/ the search engines and such. Now using the templates and such, build your site. A blog is a piece of cake to do.
Once the blog is built, go back to the dot com and under the options, put in the blog address (yourname.wordpress.com) in as the forwarding address.
Now when people type in your dot com, they are taken to your blog aka your site. You have up to 3 gigs of free space for pictures, text, links, etc. Can embed videos from Google or YouTube among other options. All easily learned in the help section of the blog.