Funny you should ask. I need to buy some to try them.

There doesn't seem to be any reliable information about how well they work on pools with salt. I can tell you (for almost certain) that tossing an anode in a plastic skimmer basket is useless. Putting one on the latter would tend to protect the ladder might, or might not protect anything else, depending on the bonding -- if you have a heavily corroded aluminum ladder anchor, or worse, a plastic anchor, you will ONLY protect the ladder.

Putting a zinc anode into the plumbing is probably useless, unless you are able to tie the anode to the pool bonding system.

The problem is that anodic protection is an ELECTRICAL process, and unless you establish the right electrical pathways, all the zinc in the world won't help a bit. Sound complicated? Apparently, it is. What I can tell you is, it's a complex subject without clear answers or established solutions.

I pestered these guys for a couple of days:
http://www.rotometals.com
and they ducked. They do big ship anodes designed and spec'd by corrosion engineers and are risk-averse. So they won't recommend ANYTHING. I'm probably going to buy these
http://www.rotometals.com/product-p/zincplate5x6x12.htm
and from them, for my own use. My personal concern is the $11,000 15HP cast iron and bronze pump I just rebuilt. This pump is on a 200,000 pool I'm converting to salt.

So, I'm going to be doing some experimenting. We'll see how it goes!

Ben