Theme: Help - The start of the unifier can also precede the first word of the themes.
20A. Behavior of a community : GROUP DYNAMICS. SUPPORT GROUP.
30A. "Star Trek" catchphrase : "BEAM ME UP". SUPPORT BEAM.
36A. Storage items near outdoor faucets : HOSE REELS. SUPPORT HOSE. (my favorite)
48A. Military officer's ride : STAFF CAR. SUPPORT STAFF.
55A. Nurturing network of family and friends, and a hint to the starts of 20-, 30-, 36- and 48-Across : SUPPORT SYSTEM
Argyle here. A Monday debut for Drew, gender unknown. I hope Splynter may find a suitable pic for SUPPORT HOSE. Two corners with 7-letter vertical stacks with the long themes connected to them. All-in-all, a good Monday debut puzzle. I hope Drew will drop by.
5. French revolutionary who was murdered in a tub : MARAT. (Jean-Paul Marat) More of a Tuesday entry.
10. Hard to outwit : WILY. Wile E. Coyote
14. Trumpet muffler : MUTE
15. Rolled out of bed : AROSE
16. One-named Gaelic folk singer : ENYA. I'll come back and link her song if I don't find anything else.
17. Bear in two constellations : URSA. Major and minor.
18. Pro cager : NBAer
19. Folksy Joan : BAEZ. I like Joan.
23. Martini liquor : GIN. Or...
24. AOL chat components : IM's. (Instant Messages)
25. Turkish __: spas : BATHS
28. 24-hour auto race city : LE MANS. South-west of Paris. 67A. 500-mile race, familiarly : INDY. Indianapolis, Indiana, a long way from France.
33. Standing straight : ERECT
34. Aim for pins : BOWL. Get 'em all, Boomer.
35. "How come?" : "WHY?". It comes after the "NO!"s of the terrible twos.
40. Satisfied sigh : "AAH!"
43. Sox player, e.g. : ALer. First basketball, now baseball.
44. Preface, briefly : INTRO
51. Attempt to cool, as steaming hot soup : BLOW ON
52. Prefix with foam : STYRO
53. Maglie or Mineo : SAL. Ball player or actor.
54. Unlock, poetically : OPE
60. Corncob pipe part : STEM
62. "The First Time __ Saw Your Face" : EVER I. Forget Enya.
63. Speech problem : LISP
64. Stay fresh : KEEP
65. Dig artifact : RELIC
66. Send out, as rays : EMIT
68. Phones on stage, e.g. : PROPS. Maybe we can get some links to when props fail. I'd look now but I probably wouldn't come back.
69. Contradict : DENY
1. Bring across the border illegally : SMUGGLE. There have been some horror stories about smuggling people.
2. One in a rush : HURRIER. Clunk! We were doing so good. Why not HARRIER?
3. "Your money's no good here!" : "IT'S ON ME!"
4. Calf meat, in Provence : VEAU. French veal.
5. Coated buttonlike candies : M AND Ms. I read it as candles; that gave me a pause!
7. Reddish horse : ROAN. 21D. Ford named for a horse : PINTO
8. On the ocean : ASEA
9. __ paper: school composition : TERM
10. Device for a Skype chat : WEBCAM. Marvelous device, I understand.
11. Very agitated : IN A STEW
12. Soap ingredient : LYE
13. '60s-'80s Red Sox legend, familiarly : YAZ. Carl Yastrzemski, member of the Baseball Hall of Fame.
22. Selectric maker : IBM
26. "Whadja say?" : "HUH?"
27. Double agent : SPY
29. "Oh" de Cologne? : "ACH". Cute clue but doesn't make up for HURRIER.
30. Drilling tool : BORER
31. Potter's pitcher : EWER. Alliteration.
32. Tavern brew : ALE
34. Lugosi who played Dracula : BELA
37. Cul-de-__ : SAC
38. Pharmaceutical giant Eli : LILLY
39. __-Globe: shakable collectible : SNO. I remember Grandma's. Today's don't cut it.
40. Balaam's mount : ASS
41. Lawyer: Abbr. : ATT.
42. Country bumpkin : HAYSEED
45. Double-cross : TWO-TIME
46. Lures by phishing, say : ROPES IN
47. Afraid of running out, gas gauge-wise : ON EMPTY
49. Drably unattractive : FRUMPY. A descriptive word.
50. Ascot wearer : FOP. FOP-a man who is excessively concerned with fashion and elegance.
51. Fundamentals : BASICS
53. Word after comic or landing : STRIP
56. Cop's suspect : PERP. Perpetrator, to a cop; perpendicular, to us.
57. Eggs __ easy : OVER
58. Move, in brokerese : RELO
59. Winter toy : SLED. Sledding is a gateway sport to skiing?
60. Tackle a slope : SKI
61. Olympic diver's perfection : TEN. On a one to ten scale.