This website is all HIIT all the time. All the workouts on this site are either body-weight only, or occasionally body-weight using very minimal equipment. An example of such equipment is a jump-rope, medicine ball, or an exercise ball. No big gym equipment required!
Use the links in the above menu to access the workouts. Note that the categories are just a starting point as many of the HIIT workouts incorporate multiple combinations of body sections, for example such as abs and upper body, etc.