Gregory's Server
A neat feature I just added: When you select the 'Call Graph' mode, Tao's compiler will automatically construct a graphviz of your program's call graph and then show it rendered inside an iframe. It's a really nice way to visualise the high-level behaviour of a program.
I am *exceedingly* bad at using web technology so the entire thing is held together with paperclips and duct tape, but it seems to do the job.