Books (IR)
http://nlp.stanford.edu/IR-book/pdf/irbookonlinereading.pdf
http://www.dcs.gla.ac.uk/Keith/Preface.html
http://it-ebooks.info/book/2816/
Books (NLP)
Natural Language Processing - A Paninian perspective
http://it-ebooks.info/book/261/
http://nlpwp.org/book/
Tools (IR)
Terrier
Nutch
Tools (NLP)
NLTK
OpenNLP