I'm trying to figure out the best way to affordably travel between a few of the destinations on my trip to Europe this April. If anyone has any advice, I would greatly appreciate it.

From Istanbul -> Santorini
and
From Athens -> Dubrovnik
and
From Dubrovnik up the coast and eventually to Zagreb. I hear since it is the off-season, ferry travel is not frequent.

If you have any details about pricing and timing, I would greatly appreciate it!

Fro the first two, try skyscanner.net. A lot will depend on how much time you have to get from place to place.

For Croatia, http://www.jadrolinija.hr/ for ferries and http://www.buscroatia.com/ for bus.

Check out www.whichbudget.com

Unless you're lucky enough to find some discount airfares I think the cheapest way to get from Istanbul to Santorini would be as follows: Bus to Marmaris; Ferry to Kos; Ferry to Santorni.

Check with Olympic Air to see what they have on offer. They recently published an email alert for some very low domestic fares.

For the Athens - Dubrovnik or Athens - Split, Croatia airlines is currently offering some tickets at € 140, which is less than half of the regular price.
http://www.croatiaairlines.com/Offer...zag&triptype=r