F# Async.Parallel

async.fs

open FSharp.Data
open System.Threading

["http://bbc.co.uk"; "http://www.google.co.uk"]
    |> List.map (fun str ->
        async {
            let! html = Http.AsyncRequestString(str)
            return sprintf "bbc len %d" html.Length 
        }
    )
    |> Async.Parallel
    |> Async.RunSynchronously
    |> String.concat ", "
    |> printfn "Lengths are: %s"