http://mararivillas.com/
Can absolutely recommend these villas, own butler, own pool (in 2 of the villas only), own beach (it feels like it it is so deserted). The food is utterly spectacular & the owners & staff cant do enough for you! Check out the Trip Advisor reviews. Don't get these mixed up with Marari Beach Resort which is a short walk along the beach, nice to spend the day at.
We stayed here
http://www.thesienavillage.com/
which I LOVED, it was up in the mountains (beware a 3 hour drive on very bumpy twisty roads!) - soo quiet and cool weather and they come and light fires in your room. Beautiful views and nice for visits to tea plantations etc.
We also stayed here
http://backwaterripples.com/
which was lovely for backwater views and trips on houseboats etc.
(Beware if you are travelling off-season (i.e. now) as a lot of resorts use these times to host big company events - the resort we stayed in was beautiful but had banging disco music from an event that took over the whole hotel until the early hours every night)
Also another beware - the packs of spices sold in strips in all the spice shops in kerala have poppy seeds in them - make sure you don't bring them back by mistake!