http://destinyghosthunter.net

You can input your gamertag and it will tell you which ghosts you have and haven't gotten yet and they have youtube guides for all the ghosts.

I'll take some cryptic hints at others, though. :P

In the Hellmouth on the way to kill Crota's soul (but it's a pre-DLC ghost).

There are a couple I've found that are WAY up there, sometimes in places you're surprised you can even go.

Hmmm... The only one lately I've found above where I thought there was going to be a barrier was in the Endless Steps area, above the hallway/valley leading out of the research station to the first portal.

I'll take some cryptic hints at others, though. :P

I think I was being haunted the other night. While playing the Archive mission, I found a Ghost up on the branches of a tree in the N/Gen branch, before you get to the actual Archive itself. For some reason, I had never thought of looking in the branches of trees before. Another mission or two on Venus and a Patrol on Mars later, I had about six or seven Ghosts in my arms, either from trees or just looking up all the time.

There are a couple I've found that are WAY up there, sometimes in places you're surprised you can even go.

At one point, I was hopping up and down on some branches declaring there was nothing there when Ragashingo told me to look down. There was one in the roots!

Obviously you can go look up their locations, but I've been just keeping an eye out while I've been playing and only have a few left now to find. Thought it was interesting. (If not, ignore me, move along, nothing to see here.)