Things to see between Edinburgh and Isle of Skye

It's really going to depend on what route you decide to take, and how long you have to do the drive to Skye, and how many days you want to spend on Skye once you get there. You could take one route to get there, and a different one to get back if you are flying in and out of Edinburgh. I would suggest flying into Edinburgh, and out of Glasgow. There are many stops and detours you can make along the way. Some of the more common ones are Stirling Castle, Eileen Donan Castle, Glen Coe, Pitlochry, Invergarry, Loch Lomand. A longer detour would take you to Oban to do a trip out to the Isle of Mull, or another would be to do the drive out to Applecross. I suggest you visit the Discover Scotland web site to get a better idea, an if you want they will do a driving route for you (for a fee) based on your interests.

Agree with Anita. There are many, many lovely places you could visit between Edinburgh and Skye -- too many to cover in a single trip. In addition to the Rick Steves guidebook, take a look at the Secret Scotland website.
https://www.secret-scotland.com/

For me it would be Glenfinnan - a stay at Glenfinnan House, a walk up to see the Glenfinnan Viaduct with the steam train crossing it, and maybe even a ride on the train itself.

How many days do you have? What is your level of physical fitness -- do you want to be out walking (Scot-speak for hiking) for hours at a time, or are you more the indoor type? Is your priority to spend time on Skye, or is that just the endpoint of your route? How thoroughly do you want to see Edinburgh?

Historical sties, picturesque towns and lovely scenery are very easy to find just about everywhere you go between Edinburgh and Skye, so no worries there.