I picked up some of the Poolife Active Cleaning Capsules which is like the HTH Duration tabs that are 68% chlorine - it's calcium hypochlorite so there's no CYA in them. They come in a plastic capsule that you can put in the skimmer but there have been warnings posted on other threads that you should not put them anywhere that pucks have been as there can be a bad reaction between different types of chlorine.

Wal-Mart carries some Duration tabs but they are only 48% chlorine and some people have said they are junk. I found the poolife ones at a poolstore that carries HTH products. I bought them mainly for when I go away but I haven't tried them yet so I can't tell you how long they last.

Peter