Not exactly a plugin but a free theme which allows your users to post from the front-end. You could customize the theme to taste or check the code and apply to your own theme.
http://wordpress.org/extend/themes/p2
Thanks, but that allows even guests to post stuff, which would be bad for spam and such.
It has no front-end member area and if people register they still see the dashboard.
You could always use user role plugins like Role Scoper http://wordpress.org/extend/plugins/role-scoper/ with P2 to control specific permissions for member groups and visitors to your site.
Based on your initial message I would probably suggest taking a look at Buddypress though http://buddypress.org/. This relies on installing WordPress Multi User, and it will give the majority of the functionality you are after, with user profiles etc.