As a DM, I’ve always wanted a tool that I could use to organize my ideas and help plan for D&D campaigns. Masterplan is the tool for which I’ve been searching these past 10 years. The interface is very functional and almost genius in its simplicity, allowing for Dungeon Masters to quickly and easily visualize the various plot points, encounters and quests they have planned.

You can also plan out dungeon maps, build encounters and treasure parcels.

This incredibly useful tool carries my highest recommendation and I’ve found it invaluable. Did I also mention that it is completely 100% free?
The author is accepting donations through paypal, so please feel free to contribute and help support this awesome work.
Check out the official site for more screenshots and details.
That’s pretty cool. You should do a post about the lessons you learned while being a DM. Something useful that new DMers should know and will probably land upon.