I was at Courtallam last weekend. Rightly called the Spa of the South, it boasts of about 9 waterfalls. The most popular of them is the Aintharuvi which separates into five small waterfalls as it hits the ground. I had a blast taking bath in one waterfall after another. Taking bath in a waterfall is a must experience for everyone. Of course, be sure that its safe. One of the falls there, Shenbagaruvi, is a 3km trek up the hills; but well worth it.
The name comes from the very fragrant Shenbaga flowers which youll find being sold near on the way to the waterfall. You may also get one free if you stopped by the Shenbagadevi temple right next to the waterfall. Beware of the monkeys. there are lots of them all over Courtallam.
Monkeys are wild animals and may get uncontrollable at times. DONT carry any food stuff when you trek etc. You may attract some uninvited guests :) The only part I didnt feel so happy about the cleanliness of the place. Though people are not supposed to use soaps, shampoos etc while taking bath not everyone obeys. Also, thanks to the small shops around, theres plently of shampoo packets and soap covers lying around.
I wish people were more responsible about their environment. Dont expect much on Accomodation and Food. You only get average lodging facilities. (costs anywhere between Rs.35 and Rs. 300). I think there is also a resort (Esakki resorts) which may provide more classy accomodation options. If you are looking for waterfalls in an isolated, wilderness place - this is not an option :)