let me just start off by saying that giving website recommendations is very difficult as there is almost no such thing as a cookie cutter website that will fit 'every' situation. so let me just elaborate on that by saying that the only way to have a website tailored to fit your exact needs is done custom by yourself or paying a respected company to do it for you...
now, for some content management systems (cms, this is what you were referring to by 'applications') there is:
) - directly for file sharing
) - open source, powerful cms
) - open source, very versatile cms
) - open source, very customizable blog-type cms
now the first one is primarily aimed towards file sharing and document sharing, the last 3 are more geared towards an all around appeal. the last three are very broad cms systems, they can be turned into almost any type of website by searching through their addons/plugins/scripts databases on their respected websites. web design and coding are very expensive, so unfortunately it is difficult to find any 'hard' advice and help to code these things by basically asking 'someone help me do this' but you will find some more love and affection by attempting to code things yourself and then asking for help after at least attempting. i hope this has brought some light to some of the difficulties you are having, post back with any feedback or further inquiries for assistance.