I am running a sandbox campaign in Greyhawk at my local FLGS. Here's the hidden secret: I'm not very creative. Here's what I've got:

1. All the 1e Greyhawk modules
2. Welsh Piper's random tables printed out in a binder
3. The 1e boxed set
4. A couple Basic modules
5. Wizard Dawn's hex-filler bookmarked.

If you have some favorite adventures/modules/other tools that you think it would behoove me to drop into this map (folks are starting in Hochoch, near the Grand Duchy of Geoff) please let me know. Really anything that makes it easier for me to let people wander around the kingdoms, making trouble, would be much appreciated.

I'm running 5e, but I'm pretty good at converting old-school material on the fly.

The 2e City of Greyhawk boxset. I notice some hate it but I thought Jean Wells' 2e Valley of the Mage was pretty damn good.

Sargent's The Night Below was originally meant for GH but was made generic at the last minute. Since it is in the Underdark it is easy to put almost anywhere. His City of Skulls is also quite good.

I'm presuming that you're OK with creating your own details and willing to consider creative aids; it isn't plug-and-play stuff already complete but instead a mass of creative starter material that gives an a high-level skeleton for you to fill in.  It does save time

1. Frog God Tome of adventure design - it has tons of stuff that makes putting creative adventures together easier and faster, including dungeon map/room design, but also more traditional module style adventures.
2. Frog God Hex Crawl Chronicles - it's generic, not set in greyhawk, but it gives tons of hex descriptions which can be ported over and used as hex starting points pretty easily
3. Land of Nod hex crawl stuff - Same as #2, by the same author, but not put out by Frog God
4. PDFs of Judges Guild stuff - again, lots of hex descriptions you can rip out, expand and use
5. Kellri's netbooks - lots of material ready to use for recurring elements such as caravans, sages, etc., that take time for a DM to do from scratch
6. JG book of treasure maps - a handful of treasure maps ready to hand out - if you're doing a sandbox campaign remember that 10% of all treasure is maps, which of course give a good reason for PCs to go from where they are now to where the treasure is at.  I'm sure there are other products also
7. A new zine coming out is The Twisted Stair which is 1E specific, and discusses world building stuff as well as giving a megadungeon level centerfold (blank) in each issue.  It's had articles expanding upon the DMG on such subjects as treasure maps, gates, doors, etc.  It's highly focused on DM tips and tricks.  

Not sure why the link button isn't working for me on this post, but the link for twisted stair is https://grodog.blogspot.com/2017/06/the-twisting-stair-2-summer-2017.html

Also, Canonfire is a GH-specific forum with a ton of stuff on it about Greyhawk.

Edit - also, although not completed, DF had a thread for filling out the D-series blank hexes.  You could lift material posted there for underground hexes

https://www.dragonsfoot.org/forums/viewtopic.php?f=42&t=18908

Quote from: Voros;970018The 2e City of Greyhawk boxset.

This is pretty amazing, despite the "suburban Milwaukee" look of the city map. Dozens and dozens of adventures, including "Vote for the Goat!"

Vote for the Goat is great, as is Ogres of the Blinding Light although it is a bit railroady but that's easy to fix.

Don't dismiss that boxed set because it's 2e. Tons of good stuff in there.
Fate if Istus, while reviled as the "Time of Troubles" for Greyhawk that handles the 1e-2e CSE, is a rather heavily plotted adventure that nonetheless takes you all over the place and has some basic maps of cities and lots of little info nuggets in certain areas.
From the Ashes, post-Greyhawk Wars is another Setting Tour, filled with campiagn ideas you can throw into the blender.

The "U" series of three adventures beginning with The Sinister Secret Of Saltmarsh - set on the coast of Keoland originally - is an excellent low-level series that, if handled well and with good players willing to role-play, lead to a very engaging and involving experience that helps to ground players in the feel of classic Greyhawk and that differentiates the setting very clearly from the other official settings.

There is a ton of good material - all the pastel 1E modules and so forth. But the most important part of any sandbox campaign is to make it your own. So, pick a county-sized area, map it in detail, dream up a few interesting NPC's, and write up the first level of your own open-ended dungeon.

I like Keoland as a starting place because it is kind of boxed in by the geography there. And I agree the 2E stuff is worth getting. Any additional exposition can't hurt. Yeah, some of the stuff is fricken cheesy. The first adventure in Treasures of Greyhawk comes to mind. But that just makes it all the more fun to modify it and make it grittier.

The swordsman challenging the party's best fighter to a dual, for example, can insist his companions throw down their weapons to ensure a fair fight... and then the rest of his gang spring out from hiding to assail the disarmed party and rob them. And instead of cheesy riddles, the gynosphinx demands to keep one of the male PCs in exchange for the information she gives. But this in itself is her test. If the group agrees to sacrifice one for the whole, she sends the party into certain death and teleports her "sacrifice" safely home. But if the group refuses, she finds them quite noble and worthy, so has them swear an oath to her in exchange for the information they seek.

Also if you have some favorite collection of small dungeons/maps/etc that you think would be appropriate dump on a few hexes in Greyhawk (e.g. Kobold Press' Book of Lairs), please let me know. This is a good time shamelessly self-promote your or a friend's work.

I know some despise it because it breaks from canon, but I think the "From the Ashes" boxed set, and some of the modules that went with it like Sargent's"Marklands" is inspired work.  A module like Marklands is great for sandboxing because there is tons of detail on minor castles, NPCs, local and regional conflicts and struggles, military forces, plots, etc.  Its almost a crossbreed between Harn and a hexcrawl.

I also like Sargent's From the Ashes work.

Ditto. I liked that whole period better than Gygax's. I know that's heresy to some old-schoolers.

Does this Greyhawk Wars business significantly alter the map? I don't really know a whole lot about things, so if it's going to be a PITA to fit 2e modules onto the 1e map, I'd rather avoid them.

Quote from: fearsomepirate;971044Does this Greyhawk Wars business significantly alter the map? I don't really know a whole lot about things, so if it's going to be a PITA to fit 2e modules onto the 1e map, I'd rather avoid them.

Not really. The main changes are:

• The Spindrift Isles (home of the L-series, my favorite series) is now a direct rip-off of the land the elves in LOTR sail off to. Fuck that shit!
• The Horned Society, Bandit Kingdoms and Barrens are part of Iuz's realm -a kind of Mordor Lite empire. Fuck that shit, too!
• The Great Kingdom is more fragmented.

One source you might want to seek out is the Greyhawk Gods as they appear in Dragon Magazine (mostly issues 65-95 or thereabouts). Not just for information about the gods, but for bits of information you can get about Greyhawk in their descriptions.