What software or online tools can detect the parts of speech in a piece of written text (e.g. to predict if a word is a verb, adjective, etc.)?
There is a web demo system called ICTCLAS (Institute of Computing Technology, Chinese Lexical Analysis System). It was developed by the Institute of Computing Technology, Chinese Academy of Science.
There is also a web demo system from THULAS (Tsinghua University - Lexical Analyzer for Chinese), which was developed by the Nature Language Processing Group, Tsinghua University.
NOTE: I don't know (and I cannot test) whether these site can be accessed freely across the world.