If you don't like vxml then here is a post on voicePHP
http://www.speechtechblog.com/2009/04/22/voicexml-to-go-down-in-the-third-says-voicephp
It's from a vendor but there might be some good ideas to get from what they
are doing.
FreeSWITCH needs demand to get vxml and it's not there yet. For now, it
looks like the FS community is waiting for demand instead of trying to
create it.