Here is a very good list originally posted by wcnwlf which I found of great help.
There are 9 to get as of course you start with one.
#01> It is the one you have at the beginning of the game
#02> Raxux Prime: There is a large area that you are out side shortly after your first encounter with Drexl. At the end of this area you'll have to hold "triangle" to charge to exit. Before you do that (while you are standing at the door) turn around. There is a platform high up on your right. You'll have to stack objects to reach it (it's just above double-jump height).
#03> Trial of Insight: Right when you get into the main temple room, it's in a pile of ruble on the left side of the stairs.
#04> Felucia: After you finish fighting the two Rancors, and you are standing at the exit, turn left. It's on a platform on the wall.
#05> Nar Shaddaa: Before you enter the second bar area, there is an arch. The hilt is sitting on top of it.
#06> Kashyyyk: Near the middle of the stage, you'll enter an area that has an oval in the middle of it that you can't walk in due to trees and other things. If you look at the mini map you'll see the oval. Just on the far side of the oval there is a hilt that is sitting on the ground between 2 guard towers.
#07> Dark Felucia: After you've gone to the top of the hill and turned around, you'll come back to the area you fight the Bull Rancor. After the fight and go to the exit it's sitting on the floor at the exit.
#08> Imperial Raxus Prime: This one was hard for me to figure out how to get. After you fight the AT-ST in the hangar, destroy the 2 control panels near the exit (this will open a door above the empty AT-ST bay). Then go to the empty AT-ST bay and double jump to the cross bar in the bay. Double jump into the door, then double jump again to get to the second level. Turn back towards the entrance. Creep out the window, then do a double-jump and dash to the ledge that is right above the entrance door.
#09> Cloud City: After you've fought the group of Mandalorians, then gone up the elevator, you'll go out side. Once you've get back inside, you'll want to destroy windows and check the ledges.
#10> Death Star: After you've crossed the tractor beam the first time (I think it's the first), there are two doors that you have to hold triangle to go through. The one that is strait in front of you holds a saber hilt. The other one leads down the path.