You probably will get a lot of recommendations, but I'll recommend the software our project group prefers, Fractal Mapper 8. It has the advantage that you can get the complete manual, which is an excellent tutorial, for free, and you can work your way through the manual and test the program free. If it's not the right software for you, you haven't lost a cent (or a pence, haleru or whatever). To download the test version, go to:
http://www.nbos.com
The test version and the full version are identical with two exceptions:
1. The test version can print the maps that you make, but it can't save them.
2. The test version comes with fewer symbols than the full version.
To get the complete manual/tutorial free, go to:
http://www.nbos.com/nox/index.php?action=1001&id=125