On this site, you will find some information on Literature you can use to determine animals and plants.
Books for the field for beginners, too.
These following books are useful for checking some species while hiking or similar, they are in German, may you have to look for books on your region and country.
These books are more in a scientific way, but if you are interested, you will learn this stuff fast.
Links to interesting stuff and identification keys online.
Nentwig W, Blick T, Gloor D, Hänggi A, Kropf C: Spiders of Europe. http://www.araneae.unibe.ch. Version of 08 May, 2016.
Siemensma, F. J. 2016. Microworld, world of amoeboid organisms. World-wide electronic publication, Kortenhoef, the Netherlands. http://www.arcella.nl; searched on 08 May, 2016.
Bugguide (USA and Canada)