Spittlebugs are the only creatures that I know of. Unless you have a serious number of them, I'd not worry about it. If just one plant is affected, you can spray the globs with water from a hose to knock the nymphs off. Insecticidal soap can help with these guys, too.

Paul, this is a year I've seen a lot perennials with spittle on them. I don't do anything and it hasn't seemed to affect anything negatively.