So you've got FreeDOS running in an x86 emulator. Or an old copy of MS-DOS 5 running on your old laptop from the mid 90s (the one where the battery doesn't hold a charge anymore). Shoot, maybe you just installed DOSBox.
The point is, you're now running DOS and you want to find some sweet games and utilities to run!
But... where the heck do you actually find them?
The Archive.org MS-DOS Library
One of the largest collections of freely downloadable DOS software is hosted by The Internet Archive (aka Archive.org).
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The DOS Games section alone contains over 8,000 entries (over 22,000 entries across all categories of software). But, as you'll quick find out, there are a heck of a lot of duplicates.
And, what's more, many of the titles available are incomplete -- sometimes missing disk images or required documentation. While Archive.org's MS-DOS Library can be an incredibly valuable resource for downloading hard to find titles... it can be a bit hit and miss.
Plus... many of the titles located there are not legal to freely distribute -- a strategy that has caused significant legal trouble for The Internet Archive with other types of content.
GOG.com
Want to get some DOS games and be sure that a) you are doing so legally, and b) you will have a complete archive of everything needed to run the game?
GOG.com is a fantastic option... assuming you're willing to spend a few dollars for each game.
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GOG -- which used to stand for "Good Old Games" -- sells (legally) a huge number of DOS titles... many of which are bundled with a copy of DOSbox to run on modern systems.
The one downside: There's no easy way to to search the GOG.com store just for DOS-only titles. Luckily, DOS gaming fans at GOG have created a forum post that lists all of the known games for sale... which use DOSbox.
In addition, many DOS games will list "This game is powered by DOSBox." in the System Requirements.
Installing DOS games from GOG, unfortunately, does require an extra step: You must first use the Windows installer to actually... you know... install the game. After which point you can copy the game contents over to your own DOS installation.
The good news? In my experience, the Windows GOG installers tend to work very well when run via WINE on Linux. So it's not too much of a headache.
DOS Software that is now Freeware
Another handy tool, is having a list of which software -- previously commercial releases back in the 80s and 90s -- has been re-released for free.
Wikipedia hosts a "List of commercial video games released as freeware" page which can be quite handy when searching for new DOS games to try.
In some cases, the inidividual game Wikipedia pages will have links to where the game can be (legally, freely) downloaded. In other cases... you'll be left to scour the web on your own. Hit and miss, but worth checking out.
Don't overlook the utilities...
A quite note.
While most people running DOS in the modern era do so to enjoy classic DOS games... I highly recommend also checking out some of the utility and productivity software availble (such as in the Archive.org MS-DOS Library).
Specifically, I'd like to draw your attention to Microsoft Word 5.5 (for DOS). Microsoft released it for free many years back and it is an absolutely delightful word processor. Highly recommended.