Son of Citation Machine helps students and professional researchers to properly credit the information they use.
Vaughan Memorial Library's "You Quote It, You Note It!" interactive tutorial
Helpful handouts for teacher use
Plagiarism dot Org
KnightCite is an online citation generator. Choose your citation style (MLA, APA or Chicago) and type of resource (book, article, chapter etc), enter in the item details and click submit. You'll get a formatted citation!
Purdue Online Writing Lab
More advanced: http://library.camden.rutgers.edu/EducationalModule/Plagiarism/citeisright.html