Purdue Online Writing Lab
A good general guide to writing, this web site also includes tips for ESL students as well as for subject specific writing.
Zotero
Zotero is a tool for collecting, managing, and citing sources. You can install it on your computer and also access your personal database of sources online.
LITS guide to Zotero. Includes information to help you download and install Zotero, as well as information for how to begin using it as your reference manager.