[mindcrime]

If you were going to found a web based start-up tomorrow, what stack would you develop in?

Depending on the details, probably some combination of:

Groovy on Grails, Tomcat, HornetQ, CentOS Linux, PostgreSQL, Redis, Memcache; with the possibility of falling back to plain Java (or even going native with C++) if necessary for performance critical stuff. If absolutely necessary, maybe Thrift for cross-platform RPC.

Note: I'm not making any claim that this is objectively the best stack available in any universal sense. But it's what would be best for me, based on what I know and am productive in.