I do not know where I would be without UAM CorpusTools (currently on version 2.4.2).
This free software allows you to create categories which you then apply to texts (or images). The results can then be searched, sorted, analysed and exported. Great for discourse analysis of any kind, but ideal for systemic functional linguistics.
Thanks to Mick O'Donnell for his hard work in constantly updating the package so that it consistently performs better and offers more functions.