Some hand-drawn work...

[psyekl]

any chance you could elaborate on the materials you use?

First and foremost: All of my maps are drawn with the intention that they will be reduced in size when they are finished. This allows a lot of leeway as far as imperfections and errors, and I think the maps always look better when they've been shrunk down a bit.
Secondly: None of these maps are from the first try: The Island has been drawn and re-drawn many, many different times and at several different scales. The treasure map is its 3rd incarnation, though I am planning on re-drawing it again.
Thirdly: The advice I give to anyone wishing to improve their skills at drawing, be it manually or digitally, is to have patience and practice, practice, practice! The greatest truth I ever learned about art was from one of my first art teachers: Being a good artist takes 10% talent and 90% practice!
The original two maps of the island are both drawn on vellum. I use non-repro blue pencil for the original sketched layout of the shorelines, mountainous areas and lakes/rivers. I then trace over lightly with 6H pencil to establish the actual lines and make any changes from the rough blue sketch. After all the lines are where I like them, I finalize it in dark HB pencil. This first drawing is called a "blank", which I keep for future reference whenever the same map (or portion therof) needs to be redrawn.
I then tape the blank down to my drawing table and lay another piece of vellum over it. Since vellum is transparent, I simply trace over the lines of my blank lightly with 6H pencil, then I use Koh-I-Noor Rapidograph technical pens for the final inking.
The final mountains (and trees on the second map) are penciled in lightly with 6H pencil and then inked when they look "right". The forests on the first map were done by stippling; that is, they are individual dots made using the .25mm (3x0) pen.
I like to mix my own ink rather than use straight black: I mix about 3 parts brown to 1 part black, this gives a more "sepia" look and cuts down the "harshness" of the technically-perfect lines the pens produce (I don't mind ultra-crisp lines on a modern or futuristic drawing, but not on my fantasy maps).
The last map was drawn on smooth surface Bristol board. Although I've used vellum almost exclusively in the past, I'm growing very fond of the way Bristol board takes ink. The ink soaks in so fast that smearing rarely occurs, where on vellum I have to wait for the ink to dry fully before being able to continue on an inked portion. Another benefit of Bristol board is that I don't have to be so careful while erasing pencil lines from an inked drawing. even careful erasing on vellum risks removing the ink.
As far as erasing goes, I use several different types of erasers depending on what I'm trying to erase: a hard white eraser for heavy blue lines, a soft white for light blue sketch lines, a soft black or hard white for 6H pencil, and an Artgum eraser held lightly for removing pencil lines from an inked surface. I even have a hard ink eraser for removing minor ink errors from vellum, though it doesn't work on Bristol board. I also use a stick eraser and a draftsman's erasing shield for precise erasing when necessary.
I haven't used wooden pencils in years, I draw with 2mm lead holders (3 to be exact: 1 each for my 6H, HB and non-repro blue leads) and .3mm, .5mm, .7mm and .9mm mechanical pencils all loaded with HB lead.
Other than my refillable Rapidograph technical pens, I also use felt-tip technical pens for any "slop" work, like filling large areas or heavy lines that don't need to be too precise.