Guile is worth mentioning here. Mature, LGPL and widely used. It supports R5RS and most of R6. It has hygienic macros. If you're looking to use a Scheme in prod

Guile is worth mentioning here. Mature, LGPL and widely used. It supports R5RS and most of R6. It has hygienic macros. If you're looking to use a Scheme in production, you probably want Guile. Stalin and Chicken Scheme might also be worth a look if you aren't faint of hearth. http://www.gnu.org/s/guile/ http://www.gnu.org/s/guile/