Purdue related

Purdue: http://www.purdue.edu/
Purdue Libraries: http://www.lib.purdue.edu/
Introductory Composition at Purdue (ICaP): http://www.digitalparlor.org/icap/
Information Technology at Purdue (ITaP): http://www.itap.purdue.edu/
The Purdue Online Writing Lab (OWL): http://owl.english.purdue.edu/
The Digital Learning Collaboratory (DLC): http://dlc.purdue.edu/

Miscellaneous writing resources

The Elements of Style by William Strunk Jr.