Linguistics research often makes use of online tools such as part-of-speech taggers and language analysis tools. The list below is not exhaustive.
CLARIN (European Research Infrastructure for Language Resources and Technology) contains many annotated resources mainly but not only in Germanic languages and tools such as a part of speech tagger. Access here CLARIN Corpora, Lexical Resources and Tools.
Linguistic Data Consortium tools. LDC develops tools to support evolving annotation tasks. All tools distributed by LDC are available at no cost under an open source license.
PRAAT phonetics software for speech analysis
Tagging and parsing tools