It sounds like what you want is a feed reader. Many sites (including BC!) offer RSS feeds of the latest of whatever the site is doing. Stock quotes, comic strips, etc. are all available in RSS form. For example,
here are some of the NYSE stock-related feeds. All modern web browsers have RSS abilities built in, or you can download a purpose-built feed reading program.
If, however, you want to embed a feed into a webpage, that too is possible. You can do it the hard way, or the easy way. I'll assume the easy way and point you here:
http://commons.ucalgary.ca/feed2js/build.php . Simple enter the RSS feed address and answer a few questions and it will spit out some javascript for you to put in your page.
But how to find a pages RSS feed address? On a site you want a feed from, look for a link that either says something like "RSS" or is an image like this one:

. That's the link to their RSS feed. Copy the address into the form I mentioned earlier or a feed reading program.
Look along the top of this page you're reading right now, for example. On the right, there are several links: Chat, Blogs, Search, Members, Help, and RSS. Clicking the RSS link will take you to a list of RSS links.
I hope this helps and hasn't been too confusing.