We're in the golden age of the Information Age but holy Orcus, there's a lot of information out there. If you are homebrewing your own campaign, there are some free amazing tools out there that can save you hours of game prep an make game night more fun for everyone. We have a couple of our own in the form of our NPC Generator and the free sample pack of our Hexplorer Digital Map Tiles. Here is the best of the best that I use for my own games. The products I mention below are all free. I have not been paid to mention them and there are no affiliate links on this page.
Fantasy Name Generator - This gem is a tool I mentioned in NPC Naming Evolution. This website contains an entire suite of random generators to name your NPCs. Among the hundreds (thousands?) of possible generators to choose from, you could pull from Dryad Names, Space Station/Colony Names, or Game of Thrones Names. These generators are guaranteed to save you time over trying to invent names off the top of your head.
Treasure Generator - Don Jon has some super useful generators optimized for specific systems such as Pathfinder, D&D 5E, and the Alien RPG. My favorite? The 5e Treasure Horde Generator. How often has the party checked the pockets of a defeated enemy and you - in a bout of mental and emotional exhaustion - offer 3d8 silver pieces. Silver is nice but what if the party instead found "a cloth coat trimmed with rabbit fur (25 gp) and a jasper cup inlaid with a meandros of electrum (25 gp)." Your players find silver coins all the time. How many jasper cups have they found? This generator is another major time saver for creating fun and memorable loot.
Encounter Calculator - Lets be real. If you have a party of 5 1st level characters, how many skeletons do you throw at them to make a hard encounter? If you said 4, I doff my proverbial cap to you. Now say you have three 2nd level PCs and, after a regrettable incident involving poor decisions and a grizzly bear, two player's lost there character and rolled up new 1st level PCs. The party encounters a Goblin Boss and three regular Goblins. Is that encounter medium, hard, or deadly? I'd need a pencil, some scrap paper, and about 10 minutes to come up with an answer that I'd be minimally confident in. Luckily, there is a website where you can plug in multiple PCs and enemies of various levels and know how difficult the encounter would be.
Monster Calculator - Did you check out our article on Reskinning Monsters and now you want to throw your abomination at the party but you have no idea what your Frankenstein-creation's challenge rating is? No worries! This web page provides both a handy chart to try to figure it out quickly, as well as a calculator where you can input your monsters stats to get an answer. One short coming is that while the calculator includes a lot of abilities your monster may have, it doesn't have all of them. The calculator is guaranteed to give you a good estimate at least and then you can use your judgement to nudge the CR up or down.
Inkarnate - This is one of my favorite tools and one I've mentioned before. Inkarnate is the best mapmaking software I've yet found. The company is constantly releasing new updates containing more art assets and new tools. You can make maps in many styles including world, regional, and dungeon in realistic and watercolor styles. The free version contains a limited assortment of assets but you can still make some great maps using it. The paid one, just $25 per year, is well worth the investment if you plan to make regular maps for your world.
There are so many great free tools out there. What is your favorite tool that I haven't mentioned? Let me know in the comments below!