The first place to start to plan a trip to Croatia is the Croatian National Tourist Board's website. In addition to a general overview of the culture and history of the country, it has lots of practical information on accommodations, travel agencies, and events. Then consult Regional Tourist Board sites to narrow the focus even further.
Croatia National Tourist Board. An excellent starting place for a broader overview of Croatia. www.croatia.hr.
Dalmatia Region. The website for Central Dalmatia. For Southern Dalmatia, see www.visitdubrovnik.hr and for Northern Dalmatia, www.zadar.hr www.dalmatia.hr.
Istria Region. www.istra.hr.
Kvarner Region. www.kvarner.hr.