Literature management for workgroups We are looking for a solution to manage our literature (citations and corresponding PDFs) in our workgroup (~15 persons). Everybody should have read-write access, so a solution having a shared library would be the best for us.

Which workflows do other groups use for a common literature management? We've checked out EndNote, Reference Manager and Mendeley so far, but are not happy with the "workgroup" options these softwares provide.
I'll go with group-level Wiki on that one. Give every member of the group read-write access (or IP-based write access), and have maintain lists of references (and attached PDF files) by topic and sub-topic. If you want to include some notes on a paper, create a new page for that paper, and put your notes there. People can add their own notes to the same paper later, by editing the page.

Search capabilities will be important, so choose you Wiki software so it has decent search support. Or export all the PDF files of papers as a read-only network drive, thus allowing for full-text search of the whole database through client's OS (which is what I do myself).

For examples of wikis run by research groups, see for example professor Hero or SklogWiki (on which papers are ordered by topic).