EDIT: can someone do me a favor and clone this in a comment so that I, hopefully, can re-clone it?
I've been playing around with constant-portfolio-allocation strategies. Due to Quantopian's lack of a "save as" button, I'm creating this as a work-around. It's just the "Live Trading" algorithm from the API docs, modified so that you don't need to allocate the same amount to each security (and written to optimize for readability). Other people may find it useful.