I seem to recall a hysterically funny (and VERY instructive) menopause thread. At the time, it was considered a classic.
Several of the threads listed here are new. A real classic is the sinners Alley thread http://talk.collegeconfidential.com/discussion/comment/8202869#Comment_8202869 (hoping that’s a link)
Also, the urban mound builders was. true classic. Can’t pull it up anymore.
Oh and here I was thinking this was a thread about cross country…
latetoschool’s and, later, sunrise east’s poignant threads really brought out the best from the cc community. latetoschool’s in particular featured some of my all-time favorite and long-gone posters, including epistrophy.
I’ve also appreciated threads in which posters speak candidly about their kids’ struggles with mental illness, addiction, and other challenges. DocT’s posts come to mind.
On the other end of the spectrum, there was a hilarious thread from a dad posting about driving his kid to college. I wish I could remember (any of) the details.
And coralbrook’s flipping threads are great!
I got some wonderful beauty product recommendations (for over 50s skin) from an earlier thread
My favorite is the “Smile and Nod” thread.
http://talk.collegeconfidential.com/parents-forum/926354-just-smile-and-nod-smile-and-nod-p1.html
My favorite is the “Say It Here” - there have been quite a few times that I really needed to say it there. While no one can respond there, I have gotten some very, very nice and supportive messages from posters I really respect and appreciate. It makes me remember that there are some very good and kind people in the world.
This thread is the best thread of all time. After all, it includes all the good ones! (@beerme, the Cal/Berkeley thread is a true classic, thanks for that link!)
The Good Buy of the Day thread is one of my favorites
http://talk.collegeconfidential.com/parent-cafe/599006-your-good-buy-of-the-day.html#latest
I am going to check out of the some of the other threads listed above.
I need to counter the post above with this one: 
http://talk.collegeconfidential.com/parent-cafe/1599005-the-bag-a-week-club.html#latest
If I am not mistaken, that was likely Curmudgeon’s post about delivering his D to Rhodes College. 
OMG the Cal v Berkeley thread is hilarious: never saw it before.
ETA: I seem to recall that the Why-is-this-a-Thread thread was hilarious . Sample contributions:
Some Guy Died
Another Guy Died
=))
Also, that may have been the thread in which I learned about the world’s best foot exfoliator…which I haven’t yet used, but I plan to someday.
Selfishly, some of my personal favorites were asking for help for specific problems. Example, my son applied to grad school during the winter of storms. He was stuck in Philadelphia airport and needed to get to new haven by 10 00 am next day. Help was offered by locals and Curmudgeon, whose dtr. Happened to be interviewing at same time. Two weekends later, son stuck in Princeton, and need to get to SF. Locals suggested he take a bus south, and fly from a different airport. People PMd me with suggestions, and in a few hours, we could rebook son’s flight and he took a train south for a few hours. None of this would have happened without the care shown by CCers.
Some fun threads were when parents asked about financial aid, at the same time asking if $500 was enough allowance per week.
I also love sharing opinions about my favorite TV shows, e.g. …British baking show, outlander, …thorns, project runway, top chef, and so on. Where else can you watch a show, and get immediate responses about outcomes and hints I missed? Oh yes, add all the threads on books.
I like the “Class of 20xx” threads. The group whose kids graduated from high school in 2010 has stuck together, through thick and thin! When my son was diagnosed with schizophrenia, they banded together to send me lots of cards and gifts. It meant the world to me. 
We still have an active Facebook group.
@Consolation… yup… Curmudgeon’s college trip was the stuff of legends. I miss him.
My vote for “most valuable” thread goes to the 2 about Andison. Andison was a high stat kid with great ECs who took a gap year when his first round of decisions was very disappointing. It is, IMO, a “must read” for the confident kid and his/her parents who are sure that great high school record guarantees some good acceptances.
Here is a link to the second, which has a happy ending.http://talk.collegeconfidential.com/parents-forum/192395-no-acceptances-one-kids-story-a-year-later-p1.html
The most hilarious thread was from the mom who said her kid wanted to be a CIA assassin and wanted advice on how to make that happen.
My favorite, by far, is the book thread. It’s been going strong for ten years now.
Most heartwarming: the story of the homeless student who was NOT accepted off the waitlist at MIT and had literally nowhere to go. I think this is the only thread that choked me up. Have tissues handy for this one!
It wasn’t the best thread of all time, but it is at least a runner-up for best thread title ever: Poodle Advice Patella Luxation I think I broke my poodle, need encouragement. http://talk.collegeconfidential.com/parent-cafe/1215764-poodle-advice-patella-luxation-i-think-i-broke-my-poodle-need-encouragement.html