Hi there,
I've not done this trip but did find a few sites that may be useful;
Cairo to Istanbul:Overview. This one seems quite thorough with lots of good info.
Personal blog:
Istanbul to Cairo OverlandTrain info for the first leg of your trip.
Gallipoli Tour, Palmyra, Cappadocia, Dead Sea, Petra, Mt. Nebo and Wadi Rum would be just some of the sights you might want to see.
I would suggest a guidebook. You're looking for quite a bit of information. Lonely Planet publishes a guidebook called
Istanbul to Cairo. You may find the overland information quite helpful as I'm sure it outlines your options quite specifically. You can get that LP used for a good price. Once you know what some of your options are, then you can explore the options for things to see along the way.

Good luck and welcome to the forums!!