Here's just a shitload of links about combinatorial species:
http://www.sinica.edu.tw/math/html/research/YNY-e.html
http://www.botik.ru/~duzhin/NMU/2000a/
http://www.mathe2.uni-bayreuth.de/frib/html/projekt/ansuchenneu_0.html
http://www.mathe2.uni-bayreuth.de/frib/html/book/hyl00.html
http://math.unipa.it/~grim/ELastaria221-230.PDF
http://www.informatics.bangor.ac.uk/~cwensley/