Contact local gyms and fitness facilities in your area and see what they offer and if they know of others. Many times such classes will have a 'drop in' rate, so you pay each time  you go (no membership or commitment to attend "X" number of classes).

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For example, through my running group I learned of a local personal trainer who held workout classes on the beach behind his home during certain months of the year. I signed up (he did have a drop-in rate as well), but finding out about him was word of mouth as he didn't really advertise in a big way. Also look up personal trainers in your area (ones not working for a specific gym) and they can likely direct you to various group classes not held at formal gyms. I have a group of friends that take a 'dance fit' class weekly, held at a local dance hall. 

Look on line at different options in your area.  Most group classes are held at a gym (membership) or a rec center.  Rec center classes may be drop-in/per-class or you may have to pre-pay for a month or the duration of the class session.

There are places like Orange Theory, that have group classes, but the per class price is pretty high.  Your area may also have yoga, Pilates, spin or CrossFit studios that specialize in those classes. You can also look up Jazzercise or Zumba and your city name to see if and where these programs are being held. 

Get off the computer and go walk around the neighborhood.