One of the most helpful websites for finding auditions is Actors Access. After creating your own account and filling out simple questions about yourself all that is left to do is to upload your head shots and resume! Now all you do is wait while casting agents put out descriptions for people they need. The computers will match you if you look like what they need or even if you play certain instrument. If you are matched and you are interested in playing the role then click it, upload one or two of your head shots that you want to submit, also if you have a slate shot or a reel upload that as well, then click submit and then the casting agents will look at all of the submissions and then from there they will let you know.
Backstage is an amazing site as well. (I have not had as much experience with this website so this will not be as in depth.) This website is know to be one of the best overall acting websites. You can apply for jobs on the site! As long as you sign-up to be a member you should get all bells and whistles it provides for you to use. Now if you are an actor please check out the link at the bottom to get more information.