A big part of the fun of old-school games is the do-it-yourself ethic behind them. One one of the most enjoyable things to do yourself (for a lot of folks, anyway) is making maps. Personally, an hour spent with the iPod on, scribing fjords and pit traps, is a great way to unwind from my often stressful and highly competetive career. Throw a couple of pints of Guinness in there, and you've got a whole evening of "de-stress"!
There are several useful resources available on the web to provide both media to do your own maps on, and actual programs that do most of the mapping for you. I'm more a fan of drawing my own maps, so I'll touch on those resources first. We'll start at farthest zoom, for continent-sized maps, and work our way inwards.
For your continental maps, you're going to want hex-paper with hundreds (or even thousands) of hexes, and you're going to want them to be kind of faded in the background, so they don't crop out your own details. Here is a customizable hex-paper generator that lets you specify how much content you want on your map. I like to set mine at .05/inch and designate the hexes at approx 10miles each, which gives me about 550x400miles per map, four of these together will let you map something roughly the size of Western Europe. This is the map for your great rivers, mountain ranges, cities, and political boundaries. Link.
Zooming in from there, you're going to want to detail certain regions in greater detail, and for that I like Grim's Blank Hex Sheets, available at the Swords and Wizardry website. Here you can get a little more up close, detailing towns, villages, hamlets, landmarks, and roads, and still keep your 10-mile hex size, and the sheet lets you detail whats in each numbered hex. Link.
In some cases, you may want even more detail than that, such as the territory around your PCs' home town, or immediately around the Megadungeon. For that, I like this map available at the Judges Guild website, which lets you detail one of your 10 miles hexes, broken down into quarter-mile hexes. Perfect for the ruined city around your Megadungeon entrance, or the noble villas and little ruins surrounding the local barons' castle. These maps are also great for detailing hexes from campaign settings you already have: I used these extensively for my last Greyhawk campaign, for instance. Link.
Lastly, you want to detail your towns and dungeons. No one size of graph paper will accomodate every function you need as a creative DM, so this customizable graph paper generator is a DM's best friend. I like 4/inch for towns, buildings, and small dungeon crawls, and 10/inch for sprawiling MegaDungeon levels. Link.
Next time I talk maps, I'll show off some good computerized mapping programs!