If you haven't received a Google+ invite by now, good luck. The service is over capacity, and it might be a while before Google invites more users into its "field test" period. However, you can still get a peek inside Google+ without an exclusive pass.
Google is indexing these public posts, and although it's not immediately obvious, anyone (including non-members) can see them. Here's how:
In Google, search for "site:plus.google.com post." This will search for all posts within Google+. If you'd like to search for posts about specific topics, like Facebook, search for "site:plus.google.com facebook."
Click on one of those links, and you'll enter Google+. From there, you can view that person's profile and search for others. Here's Declan's:
From here, you can view users' circles, explore posts, look at profiles, and quietly observe while you wait for an invite to make its way to your inbox.