To get to Kos you would first need to get to Bodrum and go from there as there is no ferry from
marmaris to Kos. Takes a couple of hours to Bodrum and then about an hour on the boat to Kos I think. If its like the ferry to Rhodes though it leaves at 9am so you would have to be up quite early to get to bodrum for 8ish in time for th boat.
Rhodes is really easy its an hour on the ferry from Marmaris which takes you to Rhodes town. From there you can exlpore Rhodes town, the harbour, old town etc or go by taxi to see some of the island such as Lindos, Ixia or Falaraki which are all quite close. If you go to the
ICR office they will help you out with the Rhodes trip and will probably be able to sort out a
transfer to the ferry port and back too.
Ephesus is about 3 hours away from
Icmeler but it it a great day out. Its a long day but I found it really interesting and quite amazing that some of the buildings and monuments were still standing after all this time! Again ICR can probably help you out with that. Most places offer Ephesus as a one day trip or as a 2 day trip where you stop over and got to see Pamukkale too. If I remember right its a limestone rock formation, but it looks like a ski resort. There is an ampitheatre there an dsome other ruins too as well as a thermal pool which you usually pay extra to swim in when you get there. I loved Pamukkale too and did it as a 2 day trip as its a more relaxed way to do it.