Erlang seems to be getting a lot of use in some of the infrastructure for scalable web apps. the CouchDB and Riak databases are written mostly in Erlang, as is the RabbitMQ message queueing server. One of the keys to its success is that it handles concurrency through message-passing, with no shared mutable state. It's this way of thinking about problems that is useful, more than any particular functional programming language.
Or, look at MapReduce. It's a very functional way of looking at computation, even if your map and reduce functions happen to be internally stateful -- and for that reason, it's a very nice fit to querying large datasets in a fault-tolerant, distributed way.
By all means, go with whatever seems most practical for you. But always keep functional programming in the back of your mind, because you never know when it might come in handy.
