phpSyntaxTree Extended Edition
While doing my minor in Linguistics, I made an extensive use of phpSyntaxTree to create my syntax and semantic trees. phpSyntaxTree is an open source web application written by André Eisenbach.
I slightly modified the PHP source to change the defaults to those I felt more relevant to the classes I was taking back then. And I also added a feature to hide the terminal branches because the textbook we were using back then (Carnie, 2006) favored this format.