http://www.img2gps.co.cc/ (March 2009)
The free program IMG2GPS is my preferred method of getting the airmaps into a gps.
Much easier to set up and use than MapSource.
It is a graphical interface, and includes Sendmap to do the dirty work.
Like others you need Garmin's USB driver if you want to use the (much quicker) usb cable on 60/76 series.
If you actually want to look at the maps before you send them to your gps, I second the recommendation of GPSMapEdit which is shareware.
Another note: the transparent maps work really well :)
