Of course, I am currently working on a site which helps contributors to add an excerpt of an article, co-authors and add a pdf related basically.
By now I managed to register and make them use my frontend dashboard by using user-meta plugin and colorbox. (Colorbox+iframe because could managed to figure out i thickbox yet). When they want to add an article they just click a link after sign-in and a colorbox opens an iframe within, with out leaving the site. You can guess the rest.
Because of the fact that the users probably will not be familiar with an admin interface, they will be confused during even this simple progress. At the beginning of the project I tried theme my login + co-authors it does not worked and I in hurry. So I solved as I told before. Now I have more time to spend on and I do not want regular registered people to deal with the admin interface. The familiar the post interface, the easier they use the site. (If you want to see the site just drop an email to gn.ozdemir[at]gmail.com)
In addition to that I am not much a coding guy. But I will give a shot if I could have some directions.