Data usage program for mobile internet?

[dougens]

i have just bought the 3mobile mobile internet dongle etc and as you cannot log into their site yet (due to mac compatibility issues) it is not possible to see how much of my 5Gb / month data usage i have used.

i have looked on th net and most folk say they use a data usage program to monitor how much of this llowance has been used.

does anyone know of a decent one to get?
preferably free??

thanks