One of the things that holds people back from using Google+ is the age old problem of finding people to follow. The Google Plus Directory is a pretty good solution to that problem. It provides a variety of different ways of finding people - by name, occupation, countries, schools, employers and so on. You can also link your Twitter and LinkedIn accounts to it as well, in order to match up with the followers on there.
I can also filter searches once I have run them. For example, there are 6,234 people who define themselves as a librarian, 159 of those are in the UK, 3,916 are female, and 36 are based in London. Having found the people that I'm interested in I can view their profiles and add them to my circles quickly and easily.
If I allow the resource access to my Google profile it can then suggest people that I might want to add to circles based on my location, my college, and similar professions. It's not a very long list, but interesting nonetheless.
Findpeopleonplus is a good tool, and one that's worth remembering when you're either looking for people to link up with on Google+ or just doing a people search.