Tools for rapid prototyping / "minimum viable product" development to use during hackathons (and beyond...)

Does anyone happen to have a list of free/low cost “rapid prototyping” and “minimum viable product” web/software production tools and services? We’re planning a hackathon, and instead of having everyone leap directly into custom coding things, I’d love to have a list that encourages people to “start with these tools that are useful and extensible before you go and build something custom”. I’m thinking things like Google Sites, Wordpress.com hosting, Survey Monkey, ArcGIS Online, etc. The Google ecosystem has so much “free” stuff, but I hate to shove people into the Google rabbit hole too much… any thoughts on good prototype/MVP production tools?

This resource has a decent list of tools - some free, some not - that could definitely be used in this way!