digg clone and charity site

we need to build a site with 5 sections to expand upon our current site. these five sections need to work together with one login/account system. we already have an xcart on this site and want to keep the accounts separate since one is for fun and one is shopping, so no need to tie in existing xcart database. we are not looking to make anything custom, but instead use a premade module on drupal or something similar. once all the functionality is working, we will skin the design with something simple and clean which we will supply. so that means the design must be completely CSS based so we can control it. here are the 5 sections: 1. [login to view URL] or reddit clone. we need users to be able to submit links and vote on the articles/images. good stories need to float to top like digg. there will only be 3 subsection upon launch but we need admin ability to create new subsections. 2. yahoo answers clone. users post questions and other users reply. good answers and good questions get voted on and float to top. 7 subsections listed in sitemap 3. photo sharing. users will be able to upload images into galleries. users will vote best photos. we will need to make more photogallery sections in admin. 4. desktop wallpaper. users will be able to upload high resolution images and then given an interface to crop and title the photo to the standard screen sizes. users will be able to vote on best desktops. browse by screen size or themes TBD 5. the last section is like the [login to view URL] - this is a site where teachers create project pages and ask for donations. on our site, we are giving the ability for non-profits organizations to create a page with description and photos. users will vote on the best projects and have the ability to donate to these projects or events. we will not handle the money but users will commit to a certain amount and record on the site. the charity will then verify once the user sends money. charity needs to be able to update project or event page with progress, photos, notes, and thank you message to donors. important notes: *we want to use amazon s3 for uploaded photo files. *please recommend the best system/cms for this project. (ex ruby on rails/drupal -- we do not like joomla!) *everything must be CSS based design so we can change art and design *google ads on the side