If you're on iOS you want the "OpenADSB" app. I think I paid $10 for it but it's awesome. It doesn't filter out the military planes like FlightRadar24 does. But, sometimes FlightRadar24 has data that OpenADSB doesn't have, so both are still useful.

A few weeks ago I was watching an F-35 off the coast of Southern California... so cool to see that stuff. It seems to also pick up weather balloons (or some kind of balloons that are above 60,000ft). Anyway, it's fun to see what's out there.