The first time I was at Koh Chang was very special, being almost on our own. The second time a lot had changed, there are ATM's now, internet everywhere, and even 7eleven opened up here. Still there are not too many tips on Koh Chang on VT yet. Therefor here a few links that can help you a lot further on accomodation and things to do on Koh Chang.
Koh Chang Online Guide
Favorite thing: Koh Chang has two basic seasons: monsoon and hot. The monsoon season starts in early June and works its way into October. For the rest of the time, visiting Koh Chang will be blue skies and hot, not that it will not be hot during the monsoon season. If you plan on visiting Koh Chang during the monsoon season GO! Mansoon doesn't mean that it will pour rain all day. For the most part it won't even rain during the day, maybe an hour so so in the afternoon. However, it normally rains at night, and rains hard at night. I was there in July and the begining of August and it was a great trip.
Koh Chang is now a cheap retreat for Thai people and backpackers. It gives beautiful beaches to the people who cannot afford suck places as Phuket, Koh Samui, or Pattaya. Right now Koh Chang is protected as a national park, but this may change soon. I heard from an American organization working in Koh Chang that the Thai Government has plans to turn Koh Chang, one of Thailand's last natural unspoiled paradises, into an expensive tourist island. This is quite scary, to be honest. We must save out Koh Chang!
Contact the Koh Chang Group for more info and to help at: firstname.lastname@example.org
This island off the eastern coast is a good alternative to Samui and Phuket if you are looking for beaches that are more low-key in nature. Also it is closer to Bangkok than the southern beaches.
There is no air transport to this island, so the only way to get there from Bkk is by bus. It is about 5 hours to Trat, and then you have to take a ferry across to the island. So, it isn't a quick trip (flying to Samui is faster), but for those of you who have more than a couple of days, Koh Chang is an excellent place to spend it.
Koh Samet is closer to Bkk (maybe 3 hours by bus plus the ferry (it is off the coast of Rayong)), but it is more crowded, esp on weekends when the Bkk crowd lets out. On long weekend, it is packed and you will be staying in a hired tent if you don't reserve accommodation.
Trat, by the way, is one of the 2 provinces in Thailand that does have malaria. So take precautions (repellents, mosquito nets). I don't recommend anti-malarial drugs - see my Thailand page under Warnings or Dangers.
Fondest memory: Please read my Koh Chang homepage for the latest news - Koh Chang as we know it may soon just be a memory. The Thai government has some big plans for this quiet island.