There are many video sharing web sites that will publish your video directly to the iTunes store. The easiest way is to upload your video to a site like blip.tv, which will automatically submit all of your work to iTunes.
If you want to do it yourself, you'll first have to create a video blog. This is the site you'll use to post your video online.
Next, set up an account with feedburner to syndicate your video blog. Feedburner adds a feature to your video blog that automatically alerts subscribers when you post new content. Once you have your feedburner account set up, you're ready to submit your video blog to iTunes.
In the podcast section of the iTunes store, select "Submit a Podcast," which will lead you through the process of getting your videos listed on the iTunes store.
Once your videos are listed on the iTunes store, anyone who's interested can subscribe and automatically download new videos every time you post them.