What exactly are ‘maps’ & ‘mini-grids’?
Dungeons Unlimited’s maps and min-grids are designed to be used with the Dungeons & Dragons 3.5 role-playing game. They serve as a visual reference for combat and encounters, allowing for DMs and players to plot and track tactical movement and area effects. In other words, they function as an illustrated, two-dimensional battlefield.
Typically, each map represents 75' by 100' of encounter area, featuring a discernable grid of 300 squares, with each square representing 5' by 5'. The maps were designed to be both generic and practical, but visually interesting at the same time. Most maps are universal in nature, allowing them to be used over and over, for a wide variety of different encounter situations.
In a nutshell, Dungeons Unlimited’s maps and mini-grids aim to improve the overall quality and efficiency of your fantasy RPG.

How do I use them?
Easy. Simply click on the map you wish to see (all maps open into new windows) and once the image is done loading, right-click to save it. Open the image with MS Paint or Photoshop or any other graphics program. Before you print the image, however, you must enlarge it slightly so that it fits to a standard 8 ˝ by 11 sheet of paper. I happen to use a program called Ulead Photo Express 2.0 to do this, but I’d imagine just about any graphics software could do it.
Once you have re-sized it, simply print it out on standard paper or cardstock. I recommend putting the map inside a clear protective sheet cover that you can purchase from Staples or Business Depot. Not only will this extend the life of your mini-map, but you can also use Dry-Erase markers over the plastic cover to indicate changes on the grid without altering the original.

How do I interpret the maps?
The maps and mini-grids feature certain terrain elements described in the Dungeon Master’s Handbook in the “Adventuring” chapter. These are explained in the “Dungeon Terrain” subsection beginning on pg. 59 and the “Wilderness Adventures” subsection beginning on pg. 87.
Some maps and mini-grids feature terrain like “Natural Stone Floors” and “Light Undergrowth” - elements which have tangible effects on combat, movement and some skill checks. If you choose to employ these terrain effects in your fantasy RPG then I suggest you review them for a more thorough understanding.
To help you interpret the maps, download the various Terrain Features Keys to serve as a quick visual reference. Theyt briefly explain the effects of various terrain elements as presented in the DMG.
Or, you could simply ignore the effects of terrain and use the maps as you see fit. It’s entirely up to you.

Are they made for D&D Miniatures?
No, although I suppose you could re-size the maps to accommodate D&D Miniatures. More than likely, re-sizing to such large dimensions would undoubtedly effect the quality of the maps.

What to use in place of miniatures?
I use wooden crafter’s spools of various sizes to represent minis. At the moment, I have spools for ‘small’, ‘medium’, ‘large’, ‘huge’ and ‘gargantuan’ creatures. I paint and number them to differentiate while on the playing field. My PCs each choose a specific color to represent their characters. You can purchase wooden crafter spools at most major craft depots or even some hardware stores. 40 spools cost me less than 15 bucks.
Ultimately, I find them to be cheaper and more versatile than D&D miniatures.