There's a few — sometimes very well hidden — places on the Internet that allow developers to host VoiceXML or CCXML applications at no charge. You can write a VoiceXML or CCXML application, place the application on a telephony server, and then call into the server and interact with the application. Here's a list of the companies that I know about that provide free hosting services to developers; if I've left one out, please feel to contact me and let me know about it.
Voxeo also offers access via 800 numbers and ordinary numbers; like most places they require access via a PIN. However you can request a unique telephone number for an application, which is convenient if you want to have other people access your demo. Voxeo also assigns each application a SIP telephone number.
What I like most about Voxeo is their "Extreme Support." Email to customer service is answered very quickly, generally within the hour, and their customer support people are very, very knowlegable. And it's also clear that their managers monitor customer support to make certain that questions are answered. Since there has never been and probably never will be a manual that answers all my questions, swift and accurate customer support is wonderful.
Tellme offers an online server for developers, but for some reason it's impossible (at least for me) to find it through their regular home page.
Tellme offers VoiceXML 2.0, tutorials, documentation, code samples, some space on their server to store application (I haven't used it much), a way to access scripts on your own server, 800 access numbers (not unique), and pre-recorded voices. You can call the server to record your own prompts.
Tellme also offers a syntax checker, which lets you check your application's syntax without actually running it.
I haven't actually tried Voicegenie's online server just yet. Voicegenie offers VoiceXML 2.0, documentation, an online syntax checker, a grammar wizard to help develop grammars, recording prompts over the phone, documentation, tutorials, sample code, and forum-based support.
Voicegenie does have some oddities. Some of their links lead to Voicegenie-supported websites that haven't been updated with developer information since 2002. And their developer agreement doesn't let developers "disclose results of any benchmark tests of such development tools to any third party without VoiceGenie Technologies' prior written approval."
BeVocal's claim to fame is that its online server has voice biometrics, such as speaker identification and verification. It makes for a nice demo (you can get one from here on my web site).
Otherwise, BeVocal offers everything: tutorials, documenation, online syntax checking, debugging tools, and a tool that lets you interact with your application in text mode. Files can be located on their server or your server. Support is via their forums, with turnaround times of up to one day.
I've used VoiceXML interpreters running on my laptop to demo VoiceXML; for example, IBM's VoiceXML interpreter downloaded from IBM Alphaworks; CCXML is available both at IBM Alphaworks and elsewhere. However, I find that running my applcations on a remote online server that's connected into the PSTN — and now SIP! — provides me with tools that otherwise simply aren't available.