SentiStrength is a sentiment analysis (opinion mining) program. SentiStrength estimates the strength of positive and negative sentiment in short texts. It is ideal for short texts like tweets.
There is an online version and a downloadable Java version which has more options. 
It is stated to be able to analyse 16,000 tweets per second. To enter multiply short test, each text has to be put on a new line. SentiStrength will give a rating of the positive and negative sentiment strength for each line in a generated text file.