Find Interesting People, Posts and Content
Looking for interesting people to follow or posts on your favorite topic? Check out the Search Google+ box on the top of the page.
Here's what you'll see when you enter a keyword in the search box. You'll notice the search results has a separate tab for people, posts, and sparks and a tab which shows a consolidated version of all three (labeled as everything).
You'll also notice the Best of/Most Recent links on the tabs labeled Everything, Google+ posts and Sparks. Best of shows the most relevant results and Most recent shows the recently posted updates.
You can click on 'Save this search' if it's a topic you would like to revisit on a regular basis. For example, I've saved searches for art keywords so I can keep track of new paintings and sketches posted on Google+. Clicking on 'Save this Search' button saves a link to the search just below the list of your circles on your left-hand sidebar.
Here are a few ideas to get you started:
Note: this only shows you public info from the profiles, so if you don't want to be found on any of these terms, edit sections of your profile and set it visible to extended circles or specific circles - check this post for instructions.
More info on search in the Google+ Help Center.