Probably lots of people don't realize it, but there's lots of discussion on this website. Click Recent Comments in the sidebar and you'll see dozens of comments from the last few days. I personally post a lot of ideas and links that way, using this site like a forum, rather than making everything a top level blog post.
Every blog post is a discussion place, even if it's years old. People find comments based on the recency of the comment, not the post, so you can comment on any topic and people will see it.
Besides using Recent Comments, you can use an RSS reader or website change tracking to get notifications about new comments. Details (scroll down to "New Comment Notifications" after the page explains how to post quotes, bold, italics, links and images).