Open RPG Maker
For Game Master's / Dungeon Masters looking for a way to create maps for free you may want to give Open RPG Maker a try.
Open RPG Maker has an interface with tiles and layers that allows you to create maps. There other even features that are not applicable to Forum Based role-playing games but you can probably use for your own entertainment. The key here is that once you've designed the map you can save it in .PNG format and then upload it.
The latest version of Open RPG Maker is 1.2 which was last compiled in December, 2012. I don't know if there is ongoing work on it but the program is usable so long as you do not try to use too many features. I'm using Windows 7 to test Open RPG Maker. There are bugs to watch for while using the program. For instance, if you use the generator to create maps then it may crash on you. Just stick with simple map creation for Play By Post games and you should be fine.
Open RPG Maker (Hover)
Attached is a quick example how Open RPG Maker can be used. A simple house with garden was created using Open RPG Maker. I added the text in with another program. I did not see a text option in Open RPG Maker but I did not look for it either.
Open RPG Maker (Hover)