Animation of the origins, insertion and action of the deltoid muscle
Here you will find a directory of muscles.
If you click on the name of a mucle listed here you will be taken to a picture of that muscle
The pictures look like simplified copies of drawings from Gray's anatomy
and they show only a part of the muscle while the origin and insertion are generally hidden behind surrounding muscles.
However it does include helpful text about origins, insertions, and actions
Loyola University Medical Education Network
Here you will find a huge list of muscles arranged alphabetically.
When you click on the name of any muscle you will see a picture of that muscle surrounded by information about its Origin, Insertion, Action, and Nerve supply.
Here you can find pictures of muscles that are superimposed on eachother in layers that you can peel away one at a time and add back one at a time.
Also there are animations for some of the muscles
showing the actions they enable a person to perform.