For some Koh Chang is the destination, for others it's the starting point for a trip to one of the more remote islands in the archipelago.  The days of arriving in Koh Wai / Koh Mak or Koh Kood by fishing boat to be greeted as a welcome distraction from hectic coconut picking by the locals is a thing of the past now. 

Over the last decade or so resorts catering to Bangkokians on package tours have sprung up on all the decent beaches.  As these resorts used to only offer all-inclusive tours which included speedboat transfers, the increase in resorts didn't necessarily mean an increase in ferry services which in turn didn't mean an increase in budget accommodation.  As if backpackers cant easily get to the islands in suitable numbers it's not worth building low cost resorts for them to stay in.

Therefore, it's only in the last couple of years that backpacker type places have opened up on these islands in any real number. 

More boat services between the islands, especially Koh Chang - Koh Wai and Koh Mak are added every year.  And late, 2008 will see the start of a new year round high speed ferry service between these islands and the mainland.  The Koh Mak page contains the times and prices for boat services in 2007-08 high season.

Koh Kood is a mini Koh Chang and is the most remote destination, although it is quickly growing in popularity, especially with tour groups from Russia.  Koh Mak with it's flat topography and clusters of small resorts on sandy white beaches is a beach bums best bet.  Whilst Koh Wai, the nearest of the islands to Koh Chang is the place to head to if you have little faith in the seaworthiness of certain ferries and therefore prefer a shorter boat journey to a quiet island where some excellent beach snorkelling exists.

There are a couple of pages of basic info on Koh Wai and Koh Mak.  But I don't know much about Koh Kood, so I'll leave that to websites such as Travelfish to cover.