If you are trying to identify, or want to know more about an invertebrate, but don't know where to start, and the list on the main page hasn't helped, then try below.
I've separated the invertebrates out by body shape, but do remember that this is just a rough and ready guide, and you won't find it in any academic textbook. Or you could try my new book availble from Amazon if it is an insect.
Smith, L. (2014). Characteristics of the insect orders. Amazon. Characteristics of the insect orders with drawings and photographs to help you understand the differences between the different types of insect, and identify which order an insect is in, as well as fast facts about each insect order, and links to web pages with more detailed information. Many orders have separate sections about the life cycle of the insect as well as its habitat requirements, and fossil history.
Things with 6 or more legs
Things that look like worms
Things that have a shell
Things that have a radial body pattern
Tiny things in water
Things that don't fit in anywhere else
If you are still none the wiser, take a photograph of it, and put it back where you found it so that it can get on with its life. Write down where you found it and what it was doing, and the date, and time of day. In fact anything you can. One day you may come across some information that leads you to an identification of the thing, or just browse around in this website, you may get lucky, and you will see just how weird and fascinating life is.
Main invertebrate page