I use great circle mapper or my routing data spreadsheet (link in the sticky *A useful reference links).
Yes - the RTWMC format is available on a web page via the "Fare Products" tab and then inside the "Round World" page. It does exactly what the RTWMC does, but obviously being a web page you don't necessarily need to download the RTWMC.
Alternatively, distances between airports is also given in the PDF format StarAlliance timetable. I find these *tend* to be more accurate re: what I actually recieve than from other sources I've tried.