Biggest Points:

1) Do you like the "Sat Style" Quasi-Photo maps? If YES, go to this tutorial: http://www.cartographersguild.com/sh...gional-RPG-Map

2) Do you like the Tolkein-esque Pen'n'Ink type maps? If YES,
Go to this tutorial by Gidde http://www.cartographersguild.com/sh...ly-Challenged)
OR
Go to this tutorial by Ascension http://www.cartographersguild.com/sh...s-in-Photoshop

Or go to all three. Other guys to keep a good eye out for on the "Antique Maps" front are: Gamerprinter, Ravells & Ramah.

If you are having issues turning a PhotoShop Tutorial into a GIMP Image, ask RobA (Seriously he should be at least St Rob of GIMP, but I'd lobby for his ascenting to godhood in GIMP. If it can be done in GIMP, RobA has done it, can do it or can write a script to make it happen anyway... [/blowing smoke up RobA's butt])