I was looking for a bus booking from Bangalore to Coorg and was really happy to find lots of post which said you can book it at http://www.ksrtc.in/.
The sign up process at http://www.ksrtc.in/ was really fast, but their search feature sucks, and I was not able to find any bus service from Bangalore to Coorg, I also tried, Bangalore - Madikeri and Bangalore - Kodagu but NO results. Finally I tried Bangalore to Virajpet, as I know that Virajpet is very close to Coorg. That search gave me the name "MERCARA", which is COORG.
So if you are looking to book tickets to Coorg on KSRTC, then search for BANGALORE to MERCARA. You will find A/C busses operating to and fro. Another strange thing on KSRTC is that if you are booking a return ticket, then your return journey can only be 5 days ahead, otherwise you cannot book return ticket !
Notes - wikipedia page -- http://en.wikipedia.org/wiki/Madikeri
