Thanks for an amazing tutorial! Once the basic principle is down, the whole process becomes very intuitive and flexible, it's great.
If you don't have access to the photoshop filters, I found it easiest to create a greyscale rippled / ocean rippled / blurred area, push it to 100% contrast and then select the white or black part - this gives you a bit of flexibility with where the edges of things are as well.
For the rivers, if you use a path with "simulate pressure" and make the path much longer than necessary you end up with a nice tapering effect (for those of us without a tablet).
Edit: A couple more variations - using clouds and an overlay colour has worked better for me than using a texture for the final 'binding' layer
http://img22.imageshack.us/img22/963/mapofdoom.th.jpg
http://img38.imageshack.us/img38/8435/mapbase06b.th.jpg
http://img682.imageshack.us/img682/9...pbase07.th.jpg

