Overleaf - The online platform for scientific writing. Overleaf is free: start writing now with one click. No sign-up required. Great on your iPad.
FileInvite - Stop chasing your clients for documents! Easily request files, documents, forms & signatures from your clients – set a due date and save hours as your requests are returned to you effortlessly.
TeXstudio - TeXstudio is an integrated environment for writing LaTeX documents.
iDeals Virtual Data Room - iDeals Virtual Data Room is a tool that provides secure access to large amount of confidential documents and can view, analyze and collaborate in a protected environment.
LyX - LyX is a document processor.
Clinked - White-label Client and Team Workspace