Forests: so simple they hurt (GIMP)
In the map (that is currently having its updated version uploaded) here, I made some pretty awesome forests (in my opinion). I had to stoop to doing something all on my own (;)) because none of the forest tutorials here worked for me. This was my answer to my struggle to find awesome forests.
The guide attached to this post will help you to do similar forests. Just don't take what I tell you as gospel, since even I can't replicate them.
Have fun with this tutorial. Get good results. Treat your GIMP well.
(If anyone could translate this to photoshop, that'd be awesome too).