First, there is a bunch of good fan materials on the Vaults of Pandius, which is dedicated to Mystara and includes Blackmoor:
Blackmoor section of Vaults of PandiusSecond, there are a ton of good adventure ideas just found on the various iterations of the Blackmoor maps and in the illustrations in the JG version of Blackmoor. The ruins of the Temple of Id are a whole adventure site, and who hasn't always wanted to go hunting for Balor eggs?
Finally, Rob Conley's Blackmarsh is a mash note to the classic Blackmoor setting, so you can get all sorts of good stuff from there, too:
Rob Conley's BlackmarshIf you are unaware, Rob wrote the two "Points of Light" books for Goodman Games. These too might provide all sorts of excellent old-school adventure ideas that can be lifted wholesale for your Blackmoor DCC campaign.
Points of Light 1Points of Light 2: The Sunrise SeaThere have also been a number of 3E, 4E, and I think even 5E releases for Blackmoor officially, by different companies, but these are all chock full of later system-style stuff, and otherwise reprise what came before, and thus may not be as useable.