I am not sure. But u can use Epi Info. 

Dear Wubengeda Admasu,

I think for making contour maps it does not matter so much what exactly you want to plot, but rather in which form you have your data, e.g. whether you have several point measurements or measurements on a grid, whether you want to plot on a very small scale or a larger one. It also matters whether you want to plot just the data or overlay ot on geographical features, such as a map, or more detailed geographical features. In the latter case, you need some GIS software, which I don't know much about.

But if you just need a simple map, with outlines of continents, or political boundaries, there is a large number of free software tools available. One that I particularly like is GMT, but one has to get used to how it works, it is not just a click and point interface. 

I forgot the link, here it is

http://gmt.soest.hawaii.edu/

you can try golden surfer 8 software and i don't know whether it is free or payable 

For contour maps Golden software Surfer is one of the best.

There is Grid Math option for regression equations and creating thematic grids,

for example for evaporation etc.

Is there a Mac-based solution out there?

Thanks Michael, let me give that a shot

Surfer, no question....

Golden Surfer has my vote, I used it heavily a couple of decades ago in the mining industry for pit and mine site contours, since them I've used it occasionally for local mapping. Proven solid software. Get the trial version, think its 10days.

Thanks Ian.