Argh there are loads. It's still a big mystery, not all are characterised and there are 'orphan' receptors and effectors which haven't been coupled up yet. You didn't even say whether you are interested in the central or peripheral nervous system.
I can help you out but it is a really big subject so if you can be more specific/ read around yourself and ask about what you don't understand.
I would really like to help you out but I could easily write a huge essay based on this and only cover a tenth of what is going on. If you post back the level you want (high school, a level, undergrad) I can go from there.
Here are some brain receptors/ effectors you can google
Dopamine, GABA, 5HT, Glutamate (NDMA, Kainate, AMPA), noradrenic, Acetyl Choline
You should also have a look at the neuromuscular junction
The Neuromuscular Junction - Learning Activity
edit - forgot to mention this textbook is really good
Pharmacology - H.P.Rang, M.M. Dale, J.M. Ritter, P. Gardner - Printed Books Shopping at dooyoo.co.uk
it starts at the beginning and is not too complicated (considering the subject matter)I know they give it to med students aswell so should be more general. But it is expensive so you might want to try the library first.
Hope this helps a bit - I just don't know where to start