Okay, I would love to get a discussion going on the recent "Guest Article":http://newbiedm.com/2009/01/13/newbiedm-tutorial-printing-battle-maps-to-a-1-scale/, because printing custom battle maps is one of my favorite things to do.
When I make mine, I often use a couple extra tricks:
# I slide the mats into mylar sheet-covers (purchasable from any office supply store). This lets me add notations to the map using wet or dry erase markers.
# When I create a custom map on one side of a sheet of cardstock, I often print a blank grid on the other. This is super useful if you don't want to give away hints as to the shape of a dungeon (e.g. meta-gamer "He drew the entrance in the southwest corner of the battle mat... This must mean all the important stuff is to the Northeast.) If your slapping down a single 8x10 grid at a time, it helps keep the party guessing. Also, if you have your party going through a maze or something, you can pull up sheets to represent their memories getting fuzzy about the path out.
I like to use free software whenever possible, and I find "Map Tool":http://www.rptools.net/index.php?page=maptool to be an excellent option for generating dungeon scale maps... though it takes some initial investment to build up a library of images. "GIMP":http://www.gimp.org/ is also an excellent choice if you've got a little more graphic-editing skill. Finally, "Dungeons Unlimited":http://www.angelfire.com/rpg2/dungeonsunlimited/ ironically provides a limited selection of ready-made layouts. I have used their stuff quite a bit also.
Okay... your turn to talk!