Familiarize yourself with these 3 lexicons:

• The Harvard Inquirer
• LIWC: Pennebaker, J.W., Chung, C.K., Ireland, M., Gonzales, A., and Booth, R.J. (2007). The development and psychometric properties of LIWC2007. Austin, TX: LIWC.net
• Sentiwordnet 3.0: Baccianella, Stefano, Andrea Esuli, and Fabrizio Sebastiani. 2010. SentiWordNet 3.0: An enhanced lexical resource for sentiment analysis and opinion mining. In Proceedings of the Seventh Conference on International Language Resources and Evaluation, 2200-2204. European Language Resources Association (ELRA).