Also included below, in a few cases, are some notable answers from an online dictionary file available here (.txt file). An asterisk denotes what one might consider a "computer victory."
Word length isn't the only criterion one might use to judge the quality of a solution. For example, word frequency might be used to break ties. (On that view, SOMEONE is better than HONOREE.) Aesthetics might also enter into it; DOVECOTE is just a more beautiful solution than LOOSENED. One solver proposed a quality scale that involves linguistic concepts such as the number of morphemes in a word. Perhaps we can ask him to identify the "nicest" solutions according to that metric in the comments section. Finally, one might argue that in the case of this puzzle, very long words are as good as very short ones, seeing as how piling letters atop one another gets harder and harder to do without adding a disqualifying vowel. (Finding such words is really CATCH-AS-CATCH-CAN...just ask any FENCINGMISTRESS or CANVAS-STRETCHER.)
In any case, the quality of the solutions was incredibly high. Many or most of the words listed below were found by two or more solvers. Moreover, you'll see that there are few computer victories. Short words conforming to the given patterns are evidently rare, yet a small group of us found many of the best possibilities. Perhaps whenever we read, we are consciously or subconsciously attending to these rather "odd-looking" words and storing them away in our minds.
Thanks for playing!
Solutions are presented in the following format: Humans first, then computer in a few cases. Each list is sorted by length, then sorted alphabetically within length (modulo clerical errors).
*1. BALACLAVA (9), CATAMARAN (9), JACARANDA (9). Notable computer answer: MAHARAJA (8)
2. AERATE (6), ACREAGE (7), MANATEE (7), ANTENNAE (8), REAPPEAR (8)
3. AIRMAIL (7), MAINTAIN (8), MAINSAIL (8), BRAINIAC (8, slangy perhaps).
*4. BOATLOAD (8), MACAROON (8). Notable computer answers: AVOCADO (7), BAZOOKA (7)
5. ARUGULA (7), AUTUMNAL (8), AVUNCULAR (9), UNFACTUAL (9).
6. ANYWAY (6), PAYDAY (6)
7. TEEPEE (6), ESTEEMED (8), EXCEEDED (8), REDEEMED (8).
8. DEITIES (7), ITEMIZE (7), IMBECILE (8), BELIEVING (9), DECEIVING (9), ILLEGIBLE (9), INSINCERE (9)
*9. HONOREE (7), DOVECOTE (8), LOOSENED (8), METRONOME (9), MONOTREME (9, jargony perhaps; anagram alert!). Notable computer answers: BOOTEE (6, if you can stomach that spelling), SOMEONE (7)
10. QUEUE (5), BURLESQUE (9), UNDERUSED (9), UNRETURNED (10). Notable computer answer: UKULELE (7)
11. BYE-BYE (6, if you can handle the hyphen), DYSENTERY (9). Notable computer answer: WHEYEY (6, archaic perhaps)
12. CIVILIZING (10), DIGITIZING (10), INFINITISM (10), NIHILISTIC (10), DIMINISHING (11)
13. COITION (7, jargony perhaps), OMISSION (8), POISONING (9), PROBIOTIC (9, used to be jargony but not really anymore), SOPORIFIC (9). Notable computer answer: OPINION (7)
*14. UNSUITING (9), FUTURISTIC (10), SUBSTITUTING (12), UNFULFILLING (12). Notable computer answers: JIUJITSU (8), RUBIDIUM (8, jargony perhaps), UMBILICUS (9, jargony perhaps)
15.YIPPILY (7, judgment call; "Well, it is how small dogs bark," argues the solver), WILLY-NILLY (10), NITTY-GRITTY (11). Notable computer answer: TYPIFYING (9)
16: VOODOO (6), COOKBOOK (8), FOOTSTOOL (9).
17: VOUDOU (6, unusual spelling), OUTPOUR (7), COUSCOUS (8), HUMOROUS (8), OUTBOUND (9), GLOBULOUS (9)
18. YO-YO (4), BOY-TOY (6, maybe a little neologistic), ROLY-POLY (8)
19. MUUMUU (6)
20. FUDDY-DUDDY (10), HURDY-GURDY (10), HURLY-BURLY (10)
21. For YYYY, one solver suggests
SYZYGYLY (suh-zi-ji-lee): In such a manner as to cause three celestial bodies to align. "The supersitious began to panic as the planets moved ever more syzygyly across the heavens."
(Seeing as computers lack humor, we win this one.)
Previous word puzzles here, here, here, and here.