I've seen a fair amount of cross-pollination, usually in Daunton landmarks and references to NPC's. One thing I liked was that there was one adventure (Daunton's Dead Shadows?) where the PC's went to the Temple of Lauto to check in with their employer, and they saw the characters from Can Dextyr Keep All These Strikers Alive running out! Another fun tie-in here is that the events of Dextyr/Strikers were explicitly the reason Mikara and Tristan got hired to join Woe and Atreus in Love Bites.
A lot of the more major overlaps tend to be in adventures done by the same DM, like how Zombies and Crooks and 6 Eagle Down dovetailed into a surprise crossover at the end. But another notably crossover is that the antagonists of Turtledome! (the owner, Mr. Pinch, and his Skull Lord lackey) became the employers of The Power of Knowledge, which as far as I know don't have any overlap in DM.
Speaking of reading all the adventures, with the start of Land Ho! yesterday, we now have as many adventures currently on-going (18!) as we have finished in history!