Well, it doesn't take too long to make a basic map. I just worked up a simple grid in Paint (making a single empty square, then copying and pasting until I had a grid-section, then copying and pasting that until I had a whole grid), then for each battle I'd copy that grid into a new file (JPG or JPEG), quickly color-code the squares to indicate what type of terrain they were (white for normal ground, green for undergrowth, dark green for thick undergrowth, light blue for shallow water, darker blue for deep water, dark gray for walls, light gray for rubble or rough terrain, blue-green for marsh/bogs, brown for obstructions like tables or whatnot, yellow or light tan for slippery ground, etc.), put a simple letter/number line along each axis of the grid so folks could designate which spaces they were moving to, and marked trees or other such objects with a large black dot with size based on how much of the square it occupied (i.e. providing light cover, full cover, etc.).
For each round of battle, I'd mark each foe's position with a letter or number (like w1 for wolf #1), and mark each PC's position with a letter or two. The map only had to be updated at the end of each round (or more accurately, after the DM handled the last NPC's action for the round, or whatever). Add a simple map-key to your post, indicating which letters indicate which PCs or NPCs and what terrain each of the current map-colors represented.
You don't need to wait for the GM to resolve each PC's action, necessarily; you can just have players post their intended actions each round, and, whenever you check the thread, you can resolve the actions of whoever posted since your last check. Of course, it can still get bogged down if some players only rarely post, or if the DM doesn't check and post every day or two or whatever (depending on what kinda pace you're trying to maintain).
