Hey all, I did a search but didn't see this mentioned anywhere. First, I don't have any affiliation with the following website... I just came across it online and thought it would be useful.
It's a free, online tool that allows you to post a map and move tokens around on it for play-by-post games. You can post the map in forums and even move the tokens around on the embedded map. Show area-of-effect spells and more.
I've just played around with it a little but it really seems like it could be a very useful tool.