Science Education Resource Center at Carleton College
Serc: Building a Protein
This hands-on activity is an assessment of the students understanding of peptide and disulfide bonds formed during protein synthesis, and the structure of an amino acid (R-group plus the common structure that all amino acids share)....
Wolfram Research
Wolfram Science World: Organic Chemistry
This site from ScienceWorld provides a brief look at some of the more common organic functional groups. The carboxylic acid group is also given. Quite a few links are provided at the bottom of the page for additional information.