Take a look for plugins, click here.
Also, how would you want to display this on your site? Do you want it a whole different section? Do you want the jokes to be displayed on a post? You could post the jokes on a post, then your viewers can also comment on your post too. And for submitting jokes, maybe they could email you on an email form and you could decide whether to accept their jokes or not?
And for your jokes rating you can use this plugin that you can put on posts, pages, comments etc. I personally use this plugin.
For most viewed jokes you can just use a most viewed posts plugin so click here to see some.