NBP-Parser is a console application that fetches data about sale and purchase rate from NBP (National Bank of Poland) and then calculates average purchase and standard deviation of selling for given currency and time range for given dates. It saves searching history in RatesHistory text file.
Example:
For EUR 2013-01-28 2013-01-31 it will give us:
Average buying rate: 4.150525
Standard deviation of selling rate: 0,0125