There are multiple ways:

• Go to the respective blog on the site!  This is probably not the answer you're looking for.
• For the QUBES blog, all recent activity is shown on the front page.
• There is a Blogs Dashboard module that will show an updated list of all QUBES, groups (of which you are a member), and member blogs.  To activate it, go to your Dashboard and click on the button Add Modules located in the upper right-hand corner, then choose the Blogs module.  Here's what it might look like:

• All blog types (QUBES, group, and member) have the capability for an RSS feed.  I say capability here as this needs to be turned on in the Settings for the member and group blogs - note that this is already available for the QUBES blog.  To turn RSS feeds on, click on the button Settings located on the specific blog page. For a group blog, you'll need to be a manager to do this.  Once the feed is active, you can access the RSS feed by clicking on the links shown below: