Holmes as a complete campaign game has been discussed for a while now - either as a standalone capped at Lvl 3, or...

Holmes as a complete campaign game has been discussed for a while now - either as a standalone capped at Lvl 3, or expanded (taking various approaches, from 3+1 capping fighters at "hero" level to ending at lvl 9 / "name level" to going out as far as Moldvay-Cook Expert did). Going complete homebrew, you'd have few problems with writing adventures for a Holmes-only campaign; but if you're short on time or just prefer modifying adventures rather than starting from scratch, you might wonder how much is really out there to use. 

Taking Holmes as a complete game with a level 3 cap, my list of adventure resources from the classic TSR era would include the following:
- the included modules B1 and B2
- T1, which although an AD&D adventure is easily converted and has a good swords & sorcery theme (small farm town threatened by evil)
- N1 (again AD&D, and like T1 a farm town threatened by evil but with a distinctly different approach)
- L1 (AD&D, but easily modded; includes a mini-sandbox wilderness area a la B1 and the Bone Hill dungeon has a different feel from the others in the list)
- B4 (B/X, again easily modified and playable as a mini-sandbox by fleshing out the underground city and caverns)
- U1 (AD&D haunted house/investigative dungeon, easily converted)
- "Temple of the Frog", from Supplement II: Blackmoor (though you'd have to depower it to avoid overwhelming TPK probability)

The old White Dwarf adventures offer some good options as well:
- "The Lichway", an ancient burial complex.
- "The Halls of Tizun Thane", investigation of a lost wizard's manse.
- "The Pool of Standing Stones", a cult of druids gone bad needs to be cleaned out from a dungeon (mid level AD&D adventure, but modifiable)
- "Grakt's Crag", a tomb complex infested with monsters and thieves (mid-level AD&D, again modifiable)
These were all collected in Best of White Dwarf Scenarios.

And Judges Guild of course had some good stuff, though much of it would need to be depowered / scaled down to fit a Holmes-only campaign; City State of the World Overlord (as an urban campaign setting), The Caverns of Thracia (large dungeon, could be expanded to a mini-sandbox and/or linked to B4) and the Thieves of Fortress Badabaskor (large dungeon) come to mind.

Any other suggestions out there?
(note that for this post, I'm intentionally limiting the range to stuff written in the AD&D 1e era and before).