Haskell has taken functional purity and ran with it. It's proof that you can eliminate side effects (sans the sin bin) and still actually get things done. The benefits of this can be seen in the papers written by SPJ, Wadler, etc. Moreover some features from Haskell/FP have influenced the mainstream programming community (Java generics).
As far as I know Erlang is not purely functional, nor does it try to be. On top of that, I think Erlang's emphasis is more on the actor model / message passing than it is on functional programming. That's my take at least.
E.g. Clean. And perhaps Curry. (Though Curry is logical-functional and nowadays compiles down to Haskell.)
There are also Spreadsheets, which are also purely functional, and even more popular to say the least but not leading. (The problem is that you can not define your own functions in Spreadsheets (without using imperative languages like Visual Basic).)
I would love a spreadsheet where the functions could be written in Lisp (or something less dysfunctional than spreadsheetese). And also one where a cell could contain any value (range of cells, functions...)
