Behringer Live Sound
If you're looking for something small and portable, start with the Eurolive B205D and Europort EPA40. The Eurolive is an all-in-one active PA monitor, so you don't need an external amp. It's great for small-venue monitoring, events and home studio use. The Europort is even more compact, and is powered by an 8-hour battery, which makes it perfect to sling over your shoulder and keep the crowd's attention when teaching or busking.
When you need a more powerful setup for an outdoor concert, conference main stage or other larger event, you'll want to take a look at Behringer's full-size monitors and power amps. These are available individually if you want to expand to an existing PA system or customize a new one from the ground up. For a simpler option, though, turn to a kit like the PMP4000/B1520 Pro PA Package. This particular bundle includes a powerful mixer, two speakers, four microphones and all the stands and cables you'll need.
Those suggestions are just a sampling of the broad range of Behringer live sound equipment. While you look at all that's available here, think about how the PA will be used and how big the crowds are. That should give you a good starting point to figure out which products or packages are right for you.