Group-Office is an enterprise CRM and collaboration tool. You can install its application on your domain in one click at SANGKRIT.net to start sharing projects, calendars, files and e-mail online with co-workers and clients. It is easy to use and fully customizable application and now it works on every SANGKRIT.net web-hosting plan.
Here are some good web services that provides you secure and scalable content sharing. You can upload files from your computer to cloud and share them with others or keep them private.
There are many web utilities that offers you invoice services, invoice is really very important if your are running a freelancing website. If you want to do it free then do it on WordPress, there are many free plugin already available in WordPress plugin repository that allows you to manage invoice and billing in your WordPress based website.