Lots
First off, I'd like to make the probably obvious point that ideally, you shouldn't pad out a saddle for the perfect fit unless as a temporary measure - and even then, only if the saddle is already too WIDE as otherwise you are narrowing the saddle...
Secondly...I have varying shimmable half pads - Mattes (lovely and thick, and wonderful quality stitching, quilting etc, but the sheepskin is a type which isn't silky imo which some don't like). Can get as normal pad, front raiser, back raiser, 4 pocket shim, 2 pocket shim...Also comes in a range of qualities of sheepskin.
Lemiuex - I have a pro-sorb half pad, which is merino sheepskin, and has a pocket running the length of the pad, each side of the spine. Lovely silky sheepskin, but not as thick as Mattes. Washes really well. I found the quilt marks quite easily is rubbed a bit though....
I also have a merino Roma full saddle cloth which is half lined with sheepskin. MUCH cheaper than the others, and comes without pockets, however I unpicked a line of stitching and replaced with velcro making 2 invisible pockets just like the other pads. Works great, cheaper option. Not washed yet. Thinner than mattes. Interestingly, absorbs sweat MUCH better than the other 2 pads from my experience so far....
HTH some... =]