Stormonu
NeoGrognard
Both of these things are true. The Dragonlance adventures were also a very good example of an Adventure Path.
Couldn't XP you, but that's another great example.
There was also:
I3-I5, the Desert of Desolation series,
I6 & I10, Ravenloft and Ravenloft 2: House on Griffon Hill,
L1-L3 - the Lenore Isle adventures,
U1-U3 - The Saltmarsh series,
T1-T4 - Village of Homlett/Temple of Elemental Evil superadventure
UK2 - UK3 - Sentinel/Gauntlet
DDA1-DDA4 - The Thyatis series
H1-H4 - Bloodstone series
During 2E days, there were also quite a few, usually for campaign worlds:
DSQ series (Road to Urik, Arcane Shadows, Asticlian Gambit)
Ravenloft: Death Ascendant, Death Triumphant, Death Unchained, (Death Undaunted)
FRE1-FRE3 - Time of troubles series
Ruins of Undermountain (I/II) + Maddgoth's Castle, Stardock & the Lost Level
Sword of the Dales, Secret of Spiderhaunt, Return of Randal Morn
Marco Volo series (Departure, Journey, Arrival)
Castle Spulzeer / Forgotten Terror crossover
The most unusual was probably Ravenloft's Feast of Goblyns, Ship of Horror, Web of Illusion, Night of the Walking Dead, Roots of Evil and From the Shadows, which shared a metaplot but couldn't easily be run as a "series"
...And I think I've listed more than enough. I'd also add that many of the boxed adventure sets were basically APs, sold en masse rather than parcelled out over several modules/books.