Free GM Resource: Hand Drawn Map Association
In-game I find two good uses for hand-drawn maps: For the GM and for the players.
As a GM I love a good map to go with my adventure. The whole "picture is worth 1000 words" rings true so often. In general I find my map needs as a GM are pretty strict because I need to use it as a tool to guide the adventure for the group.
As a player I really dig a map as a handout. Cool props make a game more interesting, as long as they aren't overused. Getting a prop/handout often requires a lot of effort on the GM's part, especially if they have to make one up during their prep time.
"A lot of effort" can mean time, but it can also mean inspiration. The Hand Drawn Map Association can really help. Essentially a large collection of hand-drawn maps that you can see online, they've just put out their first book (on their website, click on the source for the graphic above, or use this link).
I've found the HDMA a great resource for seeing different styles of (often) real maps. If nothing else, it makes me feel better about my own chicken-scratches......