Gatortailale,
They work great for attaching small frags of SPS and, for the most part, I would say that they tend to be safe, if applied correctly. My only main advice, when using super glue, is to not put the glued piece instantly inside tank. Let it cure inside a small container filled with tank water for 20 mins min. I found that some glue need time to fully cure and if put directly let's say in a small tank, fish tend to be disoriented and act eradically(happened to me once, fortunately no fish was lost). Now where to get it, you can purchase it at any hobby store, etc... Hope this helps and goodluck.
Lunasea