google-docs-bibtex-cite
This is what you have waited for: use BibTeX citations in Google Docs
Usage:
Open any google spreadsheet (or create a new empty spreadsheet)
Install script by using the menu Tools > Script Editor ...
In the editor menu go to Resource > Current script's triggers > Add new trigger
Choose: onInstall, From spreadsheet, On open (this should be the default) and save
Reload the spreadsheet, BibTeX-cite menu should appear
Use the menu BibTeX-cite > Configure BibTeX-Cite
Upload a .bib file, reload Configure BibTeX-Cite, choose .bib file and Document
Insert \cite{foo} in your Google Document
Use the BibTeX-cite > Update Citation Index