Something fun I like to do when I'm short on prep time for our Sunday night sessions is run through the RPGNow Freebie category (Your Games Now is another good place for this). Within a few minutes, I can likely find a few things to use or inspire that a) can likely be printed off in a few pages, or can just be jotted in my notes, b) is likely obscure enough that it will be brand-new to my players , and c) did I mention this is the freebie category?
This week's gem was: C&C DB1A The Haunted Highlands Map, by Troll Lord Games. My players are just getting into some rugged terrain I did not anticipate, and this actually fit closely in the geographic sense for that area. With only a little slapdash modding, I was ready to go, and looked like I had some semblance of a plan for a week when I had ZERO prep time.
I find that this is an especially excellent way to procure maps or encounters when you really are just at a loss for what's going to challenge your group.
I will add this has led to my purchasing products, when a free demo or product line freebie has really impressed me with its usefulness. So let's call it win-win, shall we?