Croatia is an amazing country - in fact it is like two countries in one. You have the coast and the islands, they have what appears to be a Venetian and Italian influence (not surprising given that at various times they were under the rule of both) and you have an area that is more central European, almost Austro-Hungarian feel, for pretty much the same reasons.
How to do justice to it all in just a week? I have been there more than once and still not seen it all and want to go back. Along the coast the favourites are Split and Dubrovnik. If you are interested in history, both are definitely worth visiting and both have within reach airports. Split is touted as the only continuously lived in Roman Palace: it started out that way but became much more. As we talk about the retirement home of the current Pope it is perhaps well to visit the retirement home of the Roman Emperor Diocletian. Not too far away are the towns of Salona (an ancient Roman city) and Trogir, an island fortress.
The drive along the coast to Dubrovnik is very scenic. There is a speedier Autoroute (or whatever it is called) but you miss the delightful bays and inlets, not to mention the lakes along the way if you stick to the high-speed road. One of the best views (for photographs) of Dubrovnik is as you head along the coast south to Cavtat and into Montenegro (Sorry to our Croatian Members, but I will plug that country for having some of the best pršut i sir). Despite the damage suffered during the wars of the 1990s the city is still an amazing example of a walled-city and no visit is complete unless you have "done the walk." If you do have time to follow the tortuous road over the mountains to Cetinje, in Montenegro, I would recommend it. Along the way you will visit Kotor, claimed to be the only fjord in the Mediterranean.
Inland visit the Plitvička jezera area. This beautiful and tranquil area of interlocking lakes and waterfalls is quite unlike any other in Europe. Keep a look out for snakes asleep in branches overhanging the lakes at the bottom of waterfalls. I am sorry but the name escapes me at the moment: perhaps a member from Croatia can prompt the memory, but nearby is a town which houses a museum dedicated to the war between Croatian and Yugoslav (officially at the time, today the may be referred to as Serbian) forces. Some of the houses still bore pock marks from bullets and shells when I was there but in a dedicated area are examples of munitions, tanks and aircraft that took part in the war. That may not be your choice of things to see but when I was there only four years ago it was still something that could not be forgotten. I vividly recall the signs along the roads warning of the dangers of mines and seeing overgrown fields and orchards, with the homesteads being gutted as the previous inhabitants fled.
The city of Zagreb is two cities (if not more ) in one. You have the old city that lies above the newer city and the suburbs. Here you will find the amazingly small parliament house (by pure chance I got to speak to a former prime Minister in the square in front of the building), the famous church with its decorative roof (displaying the arms of Croatia) and a house where Tesla lived. I recall that in the lower city, not far from Ban Jelačić Square, a tour guide intoned that Croatia had never had a problem with antisemitism. Maybe, maybe not, but within a few metres on a wall was a plaque commemorating the torching of the local synagogue in the 1940s. Be that as it may,every country has its history, both good and bad, and Croatia is no exception. Be that as it may, it is still a country worth visiting and enjoying.
Please note in this, I am not apportioning blame or criticising: I am merely reporting what I saw. Today, with additional years passed things may be different. What remains constant is that there is so much to see and do. I do hope that you enjoy your travels there.
[Edited 2013-02-14 10:53:41]