Let me recommend our product developed exactly for this goal http://www.cro-code.com/textanz.jsp
Textanz calculates frequencies of single words, phrases or wordforms. There is a possibility to sort results by length, frequency, alphabetically etc. You can also export results to external file (CSV).
Well there is no much to say here - you are welcome to visit a product page, see screenshot and try this tool.
Registered users receives version updates without additional charge. Next version is coming soon with concordance calculator (shows all words in context, including frequency=1).