I recently completed 4 weeks of FIT CHICKS bootcamp classes and loved it. They offer high intensity interval training combined with strength. In the summer the classes move outdoors but in winter they are held indoors.
The classes were really welcoming to people of all abilities. There were always ways to modify exercises to make it harder or easier depending on your level of fitness.
I was already a fit person, I completed a marathon before joining the program, but I still saw results. A full inch off my waist in 4 weeks.