Biwascheme and lips are fine projects but I don’t favour using them for the “Try Scheme” link as this might give the wrong impression to newcomers because these systems don’t implement Scheme to a sufficient level of conformance to really show off the special features of Scheme (such as tail calls, first class continuations, full numeric tower, delayed evaluation, and newer features of R7RS).  It is essential that these features be fully supported to give a good experience.