+1. It was insanely thrilling to witness this mystery unfold before our eyes in real-time.
Many of my favorites have already been mentioned. There are a bunch of collection threads I follow religiously. Some are just entertaining to read, some are awe-inspiring, some of the older ones are like time capsules. Instead of linkning every single one, I’ll refer you to the The Index of Elite Fourum Collections by @brendantheclayboy. The sheer amount of work that went into that behemoth of a thread must be insane.
Another great one (coincidentally also by Brendan) was the e4 Art Contest.
Special shoutouts to @qwachansey, @prochaos, @pichufan and of course @quuador. So many of their threads are really valuable and insightful.
Lastly, @randox 's Sales Data for 2003-2007 EX PSA 9/10 Cards. Always a nice, spirited discussion in there, even though I don’t really collect these cards myself.