Easy to follow, very practical, suited to people with limited or zero Python experience. Free version of book available online.
Natural language processing with Python
All the examples are in Python and the NLTK package but the general ideas may be of interest to users of R.
The following slides give a good brief introduction to NLTK - what you can do with it with some useful details, for example what is the difference between word_tokenize and wordpunct_tokenize.
Good source of example code, datasets and competitions: Kaggle
Kaggle has become one of the leading online resources for people who want to learn data science/data analysis.