tools like cached flow

Its called 'netflow', and you can find collectors which aggregate that data (you type a few commands into the IOS to export the netflow/cache- flow data to the collector). The tools (ManageEngine, Solarwinds, to name two) will then give you a web gui to view the data and splice it how you like. Of course almost all netflow tools are not free, but there may be a few out there (ntop was one, not sure if its still around) that are cost free.

ntop is still being actively developed and I have a customer using it who is very happy with what it does, namely provide a 'top'-like view of a network. If you want periodic reporting or long term analysis, look elsewhere.