Thorough description of abstract components - http://www.ece.cmu.edu/~koopman/essays/abstract.html
Good tips on writing a good abstract - http://darwin.bio.uci.edu/~sustain/Abstract.html
Common problems in abstracts - http://www.languages.ait.ac.th/el21abst.htm
Abstract formatting - http://www.sccur.uci.edu/sampleabstracts.html
Abstract worksheet - http://www.uaf.edu/csem/ashsss/abstract_writing.html
Sample abstracts by major disciplines - http://research.berkeley.edu/ucday/abstract.html
Multiple resources on discipline-specific abstract writing guides, posters, and oral presentations - http://www.sacnas.org/confnew/confclient/presentationResources.asp